Sickle Cell Disease and Thalassaemia

Sickle cell disease and thalassaemia are inherited disorders of haemoglobin. Sickle cell disease changes haemoglobin structure, causing haemolysis and blood vessel obstruction, while thalassaemia reduces alpha or beta globin production. Carrier states are generally not the disease, but they remain important for reproductive planning and accurate interpretation of blood tests.

Haemoglobin carries oxygen Haemoglobin is the oxygen binding protein inside red blood cells. Each molecule is built from four globin protein chains, each surrounding an iron containing haem group. Oxygen binds to the haem iron in the lungs and is released within tissues. The type and amount of globin chains change during development. This allows fetal blood to obtain oxygen across the placenta and adult blood to function after birth. Sickle cell disease and thalassaemia are inherited haemoglobin disorders. Sickle cell disease changes the structure and behaviour of haemoglobin, while thalassaemia reduces production of particular globin chains. Adult and fetal haemoglobin The main adult haemoglobin is haemoglobin A, usually shortened to HbA. It contains two alpha chains and two beta chains. Haemoglobin A2 contains two alpha and two delta chains and forms a small proportion of adult haemoglobin. Fetal haemoglobin, called HbF, contains two alpha and two gamma chains. HbF binds oxygen more strongly than HbA and is the dominant haemoglobin before birth. After birth, gamma chain production falls and beta chain production rises. This transition explains why severe beta globin disorders often become clinically apparent during the first months of life rather than immediately at birth. Globin genes The alpha globin chains are mainly produced from four genes, two inherited from each parent. The beta globin chain is produced from one HBB gene inherited from each parent. A change affecting the HBB gene can create a structural variant such as haemoglobin S or reduce beta chain production as in beta thalassaemia. Alpha thalassaemia usually results from deletion or reduced function of one or more alpha globin genes. Severity depends on how many genes are affected and how they are arranged across the two chromosomes. Recessive inheritance Sickle cell disease and clinically significant beta thalassaemia are usually inherited in an autosomal recessive pattern. A person who inherits one usual beta globin gene and one altered gene is generally a carrier. This is also called having a trait. When two carrier parents have a child, each pregnancy usually has a 25% chance of an unaffected child, a 50% chance of a carrier child and a 25% chance of a child with the relevant recessive disorder. These probabilities restart with every pregnancy. Previous children do not change the genetic chance for the next pregnancy. Alpha thalassaemia inheritance is more complex The simple 25%, 50%, 25% explanation does not describe every alpha thalassaemia pairing because four alpha globin genes are involved. Two affected genes can be inherited on the same chromosome, called cis arrangement, or one on each chromosome, called trans arrangement. The arrangement changes the reproductive risk. For example, parents carrying cis alpha zero deletions can be at risk of a pregnancy with no functioning alpha globin genes. Specialist genetic interpretation is therefore important rather than applying one inheritance diagram to every alpha thalassaemia result. Carrier or trait is not the same as disease A carrier has an altered haemoglobin gene but generally does not have the corresponding disease. Sickle cell trait does not usually cause chronic haemolytic anaemia, repeated vaso occlusive crises or the organ complications of sickle cell disease. Beta thalassaemia trait and alpha thalassaemia trait usually cause no symptoms or only mild microcytic anaemia. They do not usually require transfusion. Carrier status remains important for reproductive planning and for avoiding inaccurate labels or unnecessary treatment. Sickle cell trait A person with sickle cell trait usually has one HbA producing gene and one HbS producing gene. Most red cells contain enough HbA to prevent the repeated sickling that defines sickle cell disease. Rare complications can occur during extreme oxygen deprivation, severe dehydration, very high altitude, intense physical effort or particular anaesthetic circumstances. These unusual risks do not make trait equivalent to sickle cell disease. Routine disease treatment is not indicated for a healthy carrier. Thalassaemia trait and inappropriate iron Thalassaemia trait commonly causes small red blood cells and a mild stable anaemia. This pattern can be mistaken for iron deficiency because both conditions reduce the mean cell volume. Iron supplements do not correct thalassaemia trait and can contribute to iron excess if taken unnecessarily for long periods. Ferritin and other iron studies should confirm iron deficiency before iron is prescribed. A person can have both thalassaemia trait and genuine iron deficiency, so the two possibilities must be assessed rather than treated as mutually exclusive. Haemoglobin analysis Haemoglobin variants and chain production patterns are assessed using methods such as high performance liquid chromatography, capillary electrophoresis or haemoglobin electrophoresis. These tests estimate the proportions of HbA, HbA2, HbF and haemoglobin variants. DNA testing can clarify uncertain results, alpha thalassaemia, rare variants and reproductive risk. A recent blood transfusion can obscure haemoglobin analysis because donor red cells contribute normal haemoglobin. The laboratory and specialist team need the transfusion history. What sickle cell disease includes Sickle cell disease is a group of conditions in which haemoglobin S is inherited with another clinically significant beta globin gene. HbSS is often called sickle cell anaemia and generally produces a severe phenotype. HbS beta zero thalassaemia produces no normal beta chain output from the thalassaemia gene and often behaves similarly to HbSS. HbSC disease and HbS beta plus thalassaemia can have milder average anaemia but still cause serious vaso occlusion, acute chest syndrome, stroke, eye disease and organ damage. The haemoglobin S change Haemoglobin S results from a specific amino acid substitution within the beta globin chain. When oxygen is attached, HbS can remain dissolved within the red cell. When HbS releases oxygen, molecules can stick together and form long rigid polymers. The amount of HbS, HbF, other haemoglobins, cell dehydration, acidity, temperature and time spent deoxygenated all influence polymer formation. Polymerisation and sickling HbS polymerisation distorts the red cell into a rigid elongated or sickle like shape. Early sickling can reverse when oxygen returns. Repeated cycles damage the membrane, dehydrate the cell and make some cells permanently rigid. Rigid cells cannot move normally through narrow vessels and are removed early from the circulation. This creates the two central processes of sickle cell disease: chronic haemolytic anaemia and episodic or persistent vaso occlusion. Chronic haemolytic anaemia Sickled and membrane damaged red cells survive for far less than the normal lifespan of about 120 days. The bone marrow increases red cell production, producing a raised reticulocyte count when it can keep pace. Haemolysis can cause pallor, fatigue, jaundice and pigment gallstones. Baseline haemoglobin varies by genotype and individual. A sudden haemoglobin fall below the person's usual level can signal splenic sequestration, aplastic crisis, hyperhaemolysis, bleeding or another acute complication. Vaso occlusion Rigid red cells, white cells, platelets and activated blood vessel lining can interact and obstruct the microcirculation. Reduced flow causes tissue hypoxia, inflammation and severe pain. Reperfusion can add oxidative and inflammatory injury when flow returns. Vaso occlusion is not simply a mechanical blockage by one sickled cell. It is a dynamic inflammatory vascular process. Repeated episodes can damage bone, lungs, brain, kidneys, spleen, eyes and other organs. Triggers are not always identifiable Dehydration, infection, cold exposure, overheating, low oxygen and major physical stress can promote sickling. Menstruation, emotional stress, sleep deprivation, strenuous exertion and surgery may contribute for some people. A painful episode can occur without an obvious trigger. The absence of a recognised trigger does not make the pain less genuine. Prevention reduces risk but cannot eliminate every crisis. Acute painful vaso occlusive episodes An acute painful episode can affect the back, chest, abdomen, arms, legs or several sites. Pain can progress rapidly and may be severe enough to impair breathing, mobility, sleep and hydration. The diagnosis is clinical after considering dangerous alternatives and complications. A normal X ray or blood test does not disprove vaso occlusive pain. Individualised care plans help clinicians use the person's effective medicines and avoid delays, repeated questioning and undertreatment. Pain must be assessed promptly NICE advises treating an acute painful sickle cell episode as a medical emergency. Pain, observations and oxygen saturation should be assessed promptly, and analgesia should be offered within 30 minutes of presentation in hospital. Medication is matched to pain severity, previous effective treatment, allergies, kidney function and risk of sedation. Pain is reassessed frequently. A person whose pain is not improving needs review for acute chest syndrome, infection, avascular necrosis, abdominal disease or another complication. Managing an acute painful episode Mild episodes may sometimes be managed at home using the person's agreed plan, oral fluids and prescribed analgesia. Hospital treatment can include paracetamol, an NSAID when safe and an opioid for severe pain. Laxatives, anti sickness treatment and monitoring may be needed. Fluid is given to correct dehydration, but excessive intravenous fluid can cause pulmonary oedema and may worsen acute chest syndrome. Oxygen is used when saturation is low or another clinical indication exists. It is not a substitute for assessment of chest pain, fever or breathlessness. Bias and inequity in pain care People with sickle cell disease can experience disbelief, stigma and delays when seeking pain relief. Repeated hospital attendance reflects a recurrent genetic disease rather than evidence that pain is fabricated. Clinicians should use objective observations without assuming that normal observations mean pain is mild. Respectful communication, rapid analgesia and access to specialist advice are patient safety measures as well as standards of humane care. Acute chest syndrome Acute chest syndrome is a new pulmonary illness in a person with sickle cell disease, usually involving a new lung infiltrate with respiratory symptoms or fever. Symptoms can include chest pain, cough, fever, breathlessness, fast breathing and falling oxygen saturation. It can begin during a painful episode and progress rapidly. It is a major cause of intensive care admission and death. Any chest symptom, fever, abnormal breathing sign or hypoxia during a sickle episode requires assessment for acute chest syndrome. Why acute chest syndrome occurs Several mechanisms can contribute, including infection, fat embolism from injured bone marrow, pulmonary infarction and reduced ventilation from pain or opioid sedation. Children more often have an infectious trigger, while adults can develop more severe disease with extensive lung involvement. The syndrome can worsen after admission even when the initial chest X ray is normal. Repeated respiratory examination, oxygen monitoring and repeat imaging are therefore important when symptoms evolve. Treating acute chest syndrome Treatment takes place in hospital and commonly includes oxygen when needed, antibiotics, careful fluid management, adequate analgesia and respiratory support. Incentive spirometry can reduce atelectasis during chest or upper abdominal pain. A simple transfusion may improve oxygen carrying capacity in selected cases. Rapid progression, severe hypoxia, extensive infiltrates or failure to respond can require urgent exchange transfusion and critical care support. Stroke risk Sickle vasculopathy can narrow or occlude arteries supplying the brain. Stroke can cause facial weakness, arm or leg weakness, speech difficulty, seizure, visual change, severe headache, loss of balance or reduced consciousness. Children with HbSS and HbS beta zero thalassaemia have a particularly important risk of ischaemic stroke. Every suspected stroke is a 999 emergency. A child or adult with sickle cell disease requires the same rapid stroke recognition as anyone else plus immediate specialist haematology input. Transcranial Doppler screening Transcranial Doppler ultrasound measures blood flow velocity in major brain arteries. Higher velocities can identify children at increased risk of a first stroke before symptoms develop. UK pathways offer annual screening from about age 2 to 16 years for children with HbSS and HbS beta zero thalassaemia, with individual assessment for other genotypes. A confirmed abnormal result leads to specialist stroke prevention treatment, commonly a regular transfusion programme or another evidence based plan. Silent cerebral injury Some children and adults develop small cerebral infarcts without an obvious clinical stroke. These lesions can affect attention, processing speed, memory and school or work performance. Normal strength and speech do not guarantee that the brain has been unaffected. Neurodevelopmental, educational and neuropsychological concerns deserve assessment rather than being attributed to motivation or behaviour. Splenic sequestration Splenic sequestration occurs when a large volume of blood suddenly becomes trapped within an enlarged spleen. It mainly affects babies and young children before repeated splenic injury has caused functional autosplenectomy. Warning signs include sudden abdominal swelling, a rapidly enlarging spleen, marked pallor, weakness, fast heartbeat, breathlessness, drowsiness or collapse. It can cause life threatening hypovolaemic shock and requires emergency hospital treatment, often including urgent transfusion. Functional hyposplenism Repeated splenic vaso occlusion damages the spleen and reduces its ability to remove bacteria from blood. This functional hyposplenism can develop early in HbSS and HbS beta zero thalassaemia. Encapsulated bacteria, particularly pneumococcus, can then cause overwhelming sepsis. A person can look only mildly unwell at first. Fever in sickle cell disease requires urgent same day assessment according to the individual's emergency plan. Penicillin prophylaxis and vaccination Children diagnosed through newborn screening are started on prophylactic penicillin in early infancy unless there is a contraindication or an alternative is needed. Duration varies with age, genotype, splenic function and local specialist guidance. Many people continue antibiotic prophylaxis long term. Routine childhood vaccinations are essential. Additional protection commonly includes pneumococcal, meningococcal and annual influenza vaccination according to national and specialist schedules. Antibiotics and vaccines reduce risk but do not make fever safe to observe without advice. Fever and infection A temperature above 38 degrees Celsius, or any increased temperature in a young child according to the local plan, requires immediate contact with the specialist or urgent service. Possible infections include sepsis, pneumonia, meningitis, urinary infection, osteomyelitis and malaria after relevant travel. Blood cultures and prompt intravenous or oral antibiotics are selected according to age, observations and clinical risk. Do not delay assessment while waiting to see whether fever settles after paracetamol. Aplastic crisis Parvovirus B19 can temporarily stop red cell production. Because sickle red cells have a short lifespan, even a brief marrow pause can cause a rapid and profound haemoglobin fall. The reticulocyte count becomes unusually low, distinguishing aplastic crisis from many haemolytic causes. Symptoms include severe pallor, fatigue, breathlessness, dizziness and collapse. Transfusion may be required while marrow production recovers. Hyperhaemolysis and delayed transfusion reactions Some people develop accelerated destruction of donor and their own red cells after transfusion. Haemoglobin can fall below the pre transfusion level, with pain, fever, jaundice, dark urine and rising haemolysis markers. Further transfusion can worsen hyperhaemolysis unless guided urgently by a specialist. The person should tell clinicians about previous antibodies, delayed reactions and their haemoglobinopathy transfusion card. Priapism Priapism is a prolonged painful erection unrelated to sexual stimulation. Sickled cells can obstruct venous drainage from the penis. Repeated shorter episodes can precede a prolonged event and can eventually impair erectile function. An erection lasting more than two hours requires urgent advice and assessment. An episode approaching or exceeding four hours is a urological emergency. Hydration, urination and gentle activity may form part of an agreed early plan, but they must not delay emergency care. Avascular necrosis Repeated interruption of blood supply can damage the bone beneath a joint surface. The femoral head at the hip and the humeral head at the shoulder are common sites. Persistent groin, hip, buttock or shoulder pain, limping and reduced movement require assessment beyond treatment as a routine pain crisis. Early disease may need MRI because ordinary X rays can remain normal. Other chronic sickle complications Chronic kidney injury can cause albuminuria, impaired concentration of urine and progressive kidney disease. Retinopathy can threaten vision, particularly in HbSC disease. Regular eye screening allows laser or other treatment before irreversible loss. Leg ulcers, pulmonary hypertension, gallstones, chronic liver disease and heart strain can develop. Bone, growth, fertility, hearing and psychological health also require long term review. Pregnancy and surgery Pregnancy increases the risk of painful episodes, anaemia, thrombosis, pre eclampsia, fetal growth problems and preterm birth. Preconception review covers medicines, partner testing, transfusion history and organ assessment. Surgery and general anaesthesia can expose a person to fasting, cold, dehydration and low oxygen. Specialist perioperative planning maintains oxygenation, warmth, hydration and pain control and determines whether preoperative transfusion is needed. Newborn screening In England, the newborn blood spot programme screens babies for sickle cell disease. Early diagnosis allows specialist referral, penicillin prophylaxis, vaccination planning and parent education before infection risk rises. A baby transfused before the routine blood spot sample requires a specific screening pathway because donor blood can mask the haemoglobin pattern. Newborn screening does not replace antenatal carrier screening or later genetic counselling. Hydroxycarbamide Hydroxycarbamide, also called hydroxyurea, is a major disease modifying treatment for sickle cell disease. It increases fetal haemoglobin, reduces HbS polymerisation and has additional effects on red cells, white cells and the vascular environment. Treatment reduces painful episodes, acute chest syndrome and transfusion need in many children and adults. It is not simply a painkiller and benefits develop over time with consistent use. Hydroxycarbamide monitoring and reproductive safety Hydroxycarbamide can suppress bone marrow, so full blood counts and dose monitoring are required. Temporary dose interruption may be needed for low neutrophils, platelets or reticulocytes. Pregnancy and conception plans require specialist discussion because hydroxycarbamide can harm a developing fetus and may affect fertility considerations. People should not stop it abruptly or avoid it because of misinformation without discussing individual risks and benefits. Blood transfusion in sickle cell disease A simple transfusion adds donor red cells and raises haemoglobin. It is used for selected severe anaemia, aplastic crisis, splenic sequestration, perioperative care and some acute chest presentations. Routine transfusion is not needed for every painful crisis or for a person's stable baseline anaemia. Raising haemoglobin too high without reducing HbS can increase blood viscosity, so the target and method are chosen by a specialist. Exchange transfusion Exchange transfusion removes some of the person's red cells while replacing them with donor red cells. It reduces the percentage of HbS without causing the same increase in viscosity or iron loading as repeated simple top up transfusion. Emergency exchange is used for selected severe acute chest syndrome, acute stroke and other life threatening complications. Automated red cell exchange can also support long term stroke prevention or severe recurrent disease. Transfusion risks Repeated transfusion can cause red cell alloantibodies, delayed haemolytic reactions, hyperhaemolysis, infection and iron overload. Extended antigen matching and specialist transfusion records reduce but do not eliminate these risks. Simple transfusions add substantial iron. Exchange transfusion usually causes less net iron accumulation. People receiving regular transfusion need monitoring for antibodies, iron loading and transfusion transmitted infection according to specialist protocols. Stem cell transplantation Allogeneic haematopoietic stem cell transplantation replaces the person's marrow with donor stem cells capable of producing non sickling red cells. It can cure sickle cell disease and thalassaemia, especially when a well matched donor is available. Risks include graft versus host disease, graft failure, severe infection, organ toxicity, infertility and treatment related death. Selection considers disease severity, age, organ health, donor availability and the person's informed preferences. Gene therapy and gene editing Gene based treatments use the person's own stem cells, which are collected and modified before being returned after intensive conditioning chemotherapy. Exagamglogene autotemcel increases fetal haemoglobin by editing regulation of the BCL11A pathway. In England, NICE managed access pathways now allow this treatment for selected people aged 12 years and over with severe sickle cell disease or transfusion dependent beta thalassaemia when transplant criteria are met and a suitable related donor is unavailable. These treatments can provide a functional cure for eligible people, but they require fertility counselling, chemotherapy, prolonged specialist care and long term safety follow up. Everyday sickle care Regular specialist review monitors growth, blood pressure, kidneys, eyes, lungs, brain, bones and transfusion complications. Adequate ordinary hydration, warmth, sleep and prompt infection care reduce avoidable triggers. Exercise is encouraged with sensible pacing, hydration and avoidance of extreme exertion or hypoxia. Travel planning covers insurance, medicines, vaccination, malaria prevention, access to care and the risks of altitude or prolonged immobility. What thalassaemia means Thalassaemia describes inherited disorders in which production of alpha or beta globin chains is reduced or absent. The imbalance leaves unmatched globin chains that damage developing and circulating red cells. Anaemia therefore results from ineffective erythropoiesis within marrow and from haemolysis after cells enter the circulation. Severity ranges from a clinically silent carrier state to lifelong transfusion dependence. Alpha thalassaemia Alpha chains are required for both fetal and adult haemoglobin, so severe alpha deficiency affects fetal life. One affected alpha gene usually causes a silent carrier state. Two affected genes usually cause alpha thalassaemia trait with small red cells and mild or no anaemia. Three affected genes cause haemoglobin H disease, which can produce chronic haemolytic anaemia, splenomegaly and episodic deterioration. Alpha thalassaemia major Loss or inactivation of all four alpha globin genes causes alpha thalassaemia major. The fetus produces haemoglobin Bart's, which binds oxygen so tightly that tissue delivery is poor. Severe fetal anaemia can cause hydrops fetalis, heart failure and death without highly specialised fetal and neonatal treatment. Pregnancies at risk need early genetic counselling because maternal complications can also be serious. Beta thalassaemia Beta thalassaemia results from reduced beta chain production. Beta zero variants produce no beta chain from the affected gene. Beta plus variants retain some production. A person with one affected beta gene usually has beta thalassaemia trait. Inheriting two significant beta thalassaemia genes can cause a spectrum from non transfusion dependent disease to transfusion dependent beta thalassaemia. Thalassaemia trait or minor Trait is usually asymptomatic and may be discovered through antenatal screening or an incidental full blood count. The MCV and mean cell haemoglobin are low, while the red cell count can be relatively high. Beta thalassaemia trait usually raises HbA2. Alpha trait may have a normal routine haemoglobin analysis and require DNA testing when confirmation is important. Trait does not become thalassaemia major later in life. Its main implications are reproductive risk and avoiding inappropriate iron. Non transfusion dependent thalassaemia Non transfusion dependent thalassaemia was previously called thalassaemia intermedia. People maintain haemoglobin without regular lifelong transfusion but may need transfusion during infection, pregnancy, surgery or worsening anaemia. Chronic ineffective erythropoiesis can cause marrow expansion, splenomegaly, gallstones, bone disease, pulmonary hypertension, thrombosis and leg ulcers. Increased intestinal iron absorption can produce clinically important iron overload even without regular transfusions. Transfusion dependent beta thalassaemia Severe beta thalassaemia becomes apparent as fetal haemoglobin falls during infancy. Symptoms can include pallor, poor feeding, irritability, poor growth and increasing abdominal size from liver and spleen enlargement. Regular red cell transfusions suppress ineffective erythropoiesis, support growth and prevent severe anaemia and skeletal expansion. Modern treatment allows many people to live well into adulthood, but safe transfusion must be paired with effective iron management. Ineffective erythropoiesis In beta thalassaemia, excess unmatched alpha chains damage developing marrow cells. Many precursors die within the marrow before becoming circulating red cells. The body responds by producing more erythropoietin and expanding marrow activity. Without adequate treatment, bones can widen and weaken, the face and skull can change, and blood cell production can extend into the liver and spleen. Regular transfusion programmes Transfusion dependent thalassaemia usually requires red cells every few weeks to maintain a planned pre transfusion haemoglobin. The aim is normal growth, activity and suppression of harmful marrow expansion rather than simply treating collapse. Careful antigen matching and a permanent antibody history reduce alloimmunisation risk. Transfusion reactions, infection surveillance and vascular access are reviewed throughout life. Iron overload is the dominant long term threat Every unit of red cells contains iron, and the body has no controlled pathway for excreting large iron loads. Regular transfusion therefore causes progressive iron accumulation unless chelation removes it. Iron deposits first in the liver and later can damage the heart, pancreas, pituitary, thyroid, parathyroids and other organs. Uncontrolled iron overload can cause arrhythmia, heart failure, cirrhosis, diabetes, impaired growth, delayed puberty, infertility and bone disease. Monitoring iron overload Serum ferritin provides a useful trend but is affected by inflammation, infection and liver disease. MRI can estimate iron within the liver and heart without a biopsy. Cardiac T2 star MRI identifies myocardial iron before symptoms or echocardiographic failure develops. Monitoring also includes liver function, glucose, thyroid and reproductive hormones, growth, puberty, bone health and cardiac assessment. Iron chelation Chelating medicines bind excess iron so that it can leave through urine or stool. Desferrioxamine is given by subcutaneous or intravenous infusion. Deferiprone and deferasirox are oral options. The medicine or combination is chosen according to iron distribution, organ function, age, pregnancy plans, adverse effects and preference. Consistent chelation is lifesaving. Supportive discussion about treatment burden is more effective than blaming people who struggle with a demanding regimen. Chelation safety Deferasirox can affect kidney and liver function and requires blood and urine monitoring. Deferiprone can cause severe neutropenia or agranulocytosis, so regular blood counts and urgent assessment of fever or sore throat are essential. Desferrioxamine can affect hearing, vision, growth and bone when exposure is excessive. The specialist team adjusts chelation to iron intake and MRI findings rather than using one dose indefinitely. Other thalassaemia complications Chronic anaemia and marrow expansion can contribute to osteoporosis, fractures and extramedullary blood cell production. Splenomegaly can increase red cell and platelet consumption. Splenectomy is now used selectively because it increases infection and thrombosis risks. Endocrine complications can affect growth, puberty, fertility, thyroid function, calcium balance and glucose metabolism. Psychological wellbeing, school, work, relationships and treatment fatigue are part of routine care. Disease modifying treatment in thalassaemia Regular transfusion and chelation remain the foundation for transfusion dependent disease. Selected adults may receive an erythroid maturation medicine such as luspatercept to reduce transfusion burden. Hydroxycarbamide can increase fetal haemoglobin and may help selected non transfusion dependent phenotypes, although response varies. These medicines do not convert a carrier state into disease treatment and require specialist selection and monitoring. Curative treatment for thalassaemia A matched donor stem cell transplant can cure thalassaemia by replacing ineffective marrow with donor stem cells. Outcomes are generally best before severe iron related organ damage develops. Gene editing therapy can allow selected people with transfusion dependent beta thalassaemia to produce enough effective haemoglobin to avoid regular transfusion. Both approaches require intensive conditioning, fertility counselling and long term follow up. Diagnosing thalassaemia The full blood count commonly shows microcytosis and a low mean cell haemoglobin. Iron studies distinguish thalassaemia from iron deficiency and identify coexistence. Haemoglobin analysis detects raised HbA2, HbF and relevant variants. DNA testing defines alpha gene deletions, beta variants and complex reproductive risk. A blood film may show target cells, hypochromia, anisopoikilocytosis and nucleated red cells in severe disease. Diagnosing sickle cell disease Newborn screening identifies most children in England before symptoms appear. Outside a screening programme, diagnosis uses haemoglobin analysis and, when needed, DNA testing. The full blood count, reticulocytes, bilirubin and blood film assess haemolysis and baseline status but do not define genotype alone. Solubility tests can detect HbS but cannot reliably distinguish sickle trait from sickle cell disease and are unsuitable as the sole diagnostic test. Mixed haemoglobin disorders A person can inherit haemoglobin S with beta thalassaemia, haemoglobin C or another variant. They can also inherit alpha thalassaemia alongside sickle cell disease or beta thalassaemia. The combined phenotype is not predicted by one label alone. HbSC, HbS beta plus and HbS beta zero disease have different average patterns but wide individual variation. Specialist interpretation avoids false reassurance based only on a higher baseline haemoglobin or a supposedly milder genotype. Partner testing A carrier result should lead to an offer of testing for the biological partner when pregnancy is planned or ongoing. The partner does not need to carry the identical variant for a clinically important disorder to occur. For example, haemoglobin S can combine with haemoglobin C or beta thalassaemia to produce sickle cell disease. Testing should be offered without assumptions based on skin colour, ethnicity or country of birth because haemoglobin variants can occur in any population. Antenatal screening In England, all pregnant women are offered screening for sickle cell, thalassaemia and other haemoglobin variants. When the pregnant woman is a carrier or has a haemoglobin disorder, the baby's biological father is offered testing where possible. At risk couples receive timely counselling about the possible outcomes and reproductive options. Screening provides information and choice. It is not a directive about whether a pregnancy should continue. Prenatal diagnosis and reproductive options Chorionic villus sampling and amniocentesis can diagnose whether a fetus has inherited a significant haemoglobin disorder. The timing, miscarriage risk, possible results and limitations are discussed before consent. Some couples consider preimplantation genetic testing with IVF, donor eggs or sperm, adoption or natural conception without prenatal diagnosis. Genetic counselling should remain non directive and respect personal, cultural and religious values. Pregnancy when you have the disease Sickle cell disease and transfusion dependent thalassaemia require specialist preconception and maternity care. Medicines, iron load, heart and liver function, transfusion antibodies and fertility are reviewed before pregnancy where possible. Sickle cell disease increases pain, thrombosis, pre eclampsia and fetal growth risks. Thalassaemia care may require changes to chelation and transfusion, with close cardiac, endocrine and obstetric monitoring. Living with an inherited haemoglobin disorder The altered gene is present from conception, but disease impact can change over a lifetime. Education, employment, exercise, relationships and parenthood are achievable with appropriate care and reasonable adjustments. Pain, fatigue and treatment burden are not always visible to other people. A written emergency plan, access to specialist haemoglobinopathy services and respect for the person's own expertise improve safety and quality of life. Prognosis Newborn diagnosis, infection prevention, hydroxycarbamide, safe transfusion and specialist monitoring have substantially improved survival in sickle cell disease. Risk remains from acute chest syndrome, stroke, infection and progressive organ damage. Modern transfusion and chelation have transformed survival in thalassaemia, while transplant and gene therapy now offer curative possibilities for selected people. Outcome varies by genotype, complications, treatment access and inequities in healthcare. A carrier state should not be given the prognosis of the disease. The central safety message Sickle cell disease and thalassaemia share an inherited haemoglobin basis but have different mechanisms and complications. Carrier states are usually not the disease and do not justify routine disease treatment or unconfirmed iron supplementation. Fever, chest symptoms, stroke signs, splenic sequestration and prolonged priapism are urgent sickle cell presentations. In severe thalassaemia, regular transfusion must be paired with iron monitoring and chelation to protect the heart, liver and endocrine organs.

Sickle cell disease and thalassaemia both arise from inherited globin gene changes, but one mainly alters haemoglobin behaviour and the other reduces globin production. Accurate genotype, emergency recognition, disease modifying care and genetic counselling prevent harm, while carrier states should not be mislabelled or treated as the disease.