We present a case of Haemoglobin H (HbH) disease detected during presentation of Idiopathic Thrombocytopenic Purpura (ITP). Concerns arise when more than one blood cell line is affected. This case demonstrates the importance of history taking and interpretation of red cell indices.
Case:A 14-month old boy presented with a two-day history of widespread petechiae and bruising. He was clinically well with no organomegaly. He had a normal birth history and Guthrie screening was performed on day five of life. He had a full and varied diet; he was thriving with height and weight between the 75th–91st centiles. Systemic examination was otherwise unremarkable. Initial blood results revealed: haemoglobin 8.7 g/dL (11.3–14.1), platelets 22 × 109/L (150–450 × 109), mean cell volume 54.4 fL (71–85), mean cell haemoglobin 14.1 pg (23–31), reticulocytes 2.1%, normal biochemistry, inflammatory markers, and coagulation. Blood film microscopy showed target cells and thrombocytopenia.
In view of the typical history for ITP and no malignant features, blood was sent for haemoglobin electrophoresis, iron studies, and leukocyte immunophenotyping. HbH disease was confirmed on electrophoresis (see figure); HbH disease with concurrent ITP was diagnosed. He was commenced on folic acid and followed up in clinic. Platelets increased over one month and ITP resolved spontaneously without treatment by four months. Parental gene testing subsequently demonstrated mother to have –-/αα and father α-/α-.
Discussion HbH occurs when there is a deletion of 3 of the 4 α-globin genes (--/-α). This leads to globin chain imbalance with accumulation of variable amounts of haemoglobin H (4β globin chains). Symptoms range from mild to severe anaemia, splenomegaly, and poor growth. The microcytic, hypochromic anaemia can be misconstrued for iron deficiency anaemia, hence the importance of a thorough dietary history and evaluation of iron studies. HbH may be detected on Guthrie screening as an abnormal band but does not meet the criteria for further investigation, unlike haemoglobin variants S, C, D, E, O Arab, and Lepore.
Treatment is supportive with folic acid and intermittent transfusion therapy. Those with HbH disease appear to lead a normal life. Genetic counselling must ensue, however prenatal diagnosis cannot predict clinical severity.
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