A child presents with eczema, thrombocytopenia, and elevated levels of IgA. What is the most likely diagnosis?

The clinical presentation of eczema, thrombocytopenia, and elevated levels of IgA in this child suggests Wiskott-Aldrich syndrome. This condition is a X-linked recessive immunodeficiency that is characterized by the triad of eczema, recurrent infections (due to immunodeficiency), and thrombocytopenia leading to an increased risk of bleeding.

In Wiskott-Aldrich syndrome, IgA levels can be elevated, but the significant identifying features are the eczema and low platelet counts. The immunological defect is related to the inability of B cells to produce specific antibodies, particularly affecting the production of IgM and the class switching to IgA and IgE, resulting in dysregulation of these immunoglobulins.

In contrast, hyper-IgE syndrome is characterized by high levels of IgE but does not typically present with thrombocytopenia or eczema in the way seen with Wiskott-Aldrich syndrome. Ataxia-telangiectasia involves neurological symptoms, immunodeficiency, and a higher risk for malignancies, and it does not characterize eczema or thrombocytopenia. IgA deficiency alone would typically not present with thrombocytopenia and often does not lead to elevated IgA levels; instead