Differentials
Idiopathic thrombocytopenia (ITP)
SIGNS / SYMPTOMS
Unlike WAS, ITP is not present from birth and is not familial. Clinical features can be very similar, as eczema is frequent in children and not all WAS patients have a significant infectious history. The existence of other affected family members suggests WAS.
INVESTIGATIONS
Platelet size below normal range for WAS.
Evidence of autoimmune basis for thrombocytopenia is not a discriminator, as this can be present in WAS as well.
Autoimmune lymphoproliferative syndrome (ALPS)
SIGNS / SYMPTOMS
ALPS may present with autoimmune thrombocytopenia. ALPS is usually associated with a history, or presence, of generalised lymphadenopathy. Lymph node enlargement in ALPS is generally much more striking and greater than that seen in WAS.
INVESTIGATIONS
Platelet size below normal range for WAS.
Double negative T-cells are raised in ALPS and normal in WAS. These double negative cells are TCR alpha-beta+CD3+CD4-CD8- and assays are available only at specialist centres.
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