A child presents with eczematous skin lesions, thrombocytopenia, immunodeficiency, and bloody diarrhea. What is the most likely diagnosis?

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Multiple Choice

A child presents with eczematous skin lesions, thrombocytopenia, immunodeficiency, and bloody diarrhea. What is the most likely diagnosis?

The key idea is recognizing Wiskott-Aldrich syndrome, an X-linked disorder that classically presents with a triad of eczema, thrombocytopenia (often with small platelets), and immunodeficiency. A mutation in the WAS gene disrupts WASp, impairing cytoskeletal signaling in blood cells, which leads to both the bleeding tendency (thrombocytopenia and easy mucosal bleeding, explaining the bloody diarrhea) and a weakened immune defense (recurrent infections and poor antibody responses). The eczema component reflects immune dysregulation. Because this condition is X-linked, it predominantly appears in boys, aligning with the described presentation. Other listed immunodeficiencies don’t fit this combination: SCID causes severe, early infections but not the characteristic eczema with low platelet counts; X-linked agammaglobulinemia features low B cells and immunoglobulins without eczema or bleeding tendencies; ataxia-telangiectasia includes neurodevelopmental issues and telangiectasias with immunodeficiency but not the eczema-thrombocytopenia pattern.

The key idea is recognizing Wiskott-Aldrich syndrome, an X-linked disorder that classically presents with a triad of eczema, thrombocytopenia (often with small platelets), and immunodeficiency. A mutation in the WAS gene disrupts WASp, impairing cytoskeletal signaling in blood cells, which leads to both the bleeding tendency (thrombocytopenia and easy mucosal bleeding, explaining the bloody diarrhea) and a weakened immune defense (recurrent infections and poor antibody responses). The eczema component reflects immune dysregulation. Because this condition is X-linked, it predominantly appears in boys, aligning with the described presentation.

Other listed immunodeficiencies don’t fit this combination: SCID causes severe, early infections but not the characteristic eczema with low platelet counts; X-linked agammaglobulinemia features low B cells and immunoglobulins without eczema or bleeding tendencies; ataxia-telangiectasia includes neurodevelopmental issues and telangiectasias with immunodeficiency but not the eczema-thrombocytopenia pattern.

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