Red blood count membrane defect anaemias
· Autosomal dominant (AD) in 75% cases. Incidence 71/5000 (northern European).
· Various RBC membrane skeletal defects occur; commonest involves ankyrin (750–60%).
· Mild to moderate anaemia in compensated cases. Anaemia can be severe with transfusion requirement.
· Splenomegaly is usually present.
· Infection exacerbates haemolysis with worsening jaundice.
· Aplastic (red cell) crisis can occur with parvovirus B19 infection. The severity of anaemia depends on degree of baseline haemolysis (worst in those with high reticulocyte counts due to sudden decompensation).
· Folate deficiency can occur with massively increased RBC turnover so oral supplementation with 5mg/day folic acid should be given routinely.
· Laboratory investigation includes: ‘rise’reticulocytes, ii spherocytes on blood film; red cell indices may be slightly low, but clue is in the MCHC, which is raised, i.e. hyperchromic due to the spherical shape of the RBCs. Direct Coombs test –ve (excludes autoimmune causes).
· In the past the osmotic fragility was performed, but now diagnosis can be made on clinical and basic haematological features of indices, reticulocytes and blood film. Diagnosis in difficult cases can be made by flow cytometry, but is expensive and usually not clinically warranted.
· Provide supportive treatment, e.g. folic acid supplementation, blood transfusion if anaemia severe during aplastic crises.
· Ideally, if splenectomy is indicated it is best performed after 5yrs of age but before puberty. Consider if:
· anaemia is not compensated and child is not thriving physically, socially, or educationally;
· chronic haemolysis resulting in gallstone formation;
· persistent jaundice is a rare indication for cosmetic reasons.
· Splenectomy requires pre-operative vaccination against pneumococcus, Haemophilus influenza type B (HiB) and meningococcus C, as well as post-operative 5-yearly boosters, annual influenza vaccination, lifelong penicillin V prophylaxis (250mg bd from 5yrs until adolescence, then 500mg bd).
Heterogeneous group of disorders with mainly AD inheritance. Incidence 1:25,000. Severity varies from asymptomatic chronic compensated haemo-lysis (majority) to transfusion dependence. Presentation and management similar to HS. Blood film shows elliptical RBCs.
In this disorder RBCs are extremely sensitive to raised temperature. Hb usually 77–9g/dL. Jaundice and splenomegaly present. Good response to splenectomy in those severely affected.
This condition has AD inheritance and is of variable severity.