Extended immune phenotype and biopsy image of the index patient. (A) White blood cell (WBC) count assessment over time showed normal white blood cell count. (B) Immunoglobulin assessment over time showed low IgG until initiation of intravenous immunoglobulin (IVIG), low/normal IgM levels, and low/normal IgA levels. (C) Skin biopsy performed at 9 years old from the left thigh. Tissue section stained with H&E showing subcutaneous necrotizing (*) and non-necrotizing granulomas (arrowhead). Specific staining for organisms was negative (not shown). Scale bar: 200 μm. (D) Micrograph of lymph node indicating juxtaposed granulomatous inflammation (*) and classical Hodgkin lymphoma with Reed–Sternberg cells (arrowheads). Scale bar: 200 μm.