Figure 1. Histologic findings from brain of 15-year-old boy with X-linked agammaglobulinemia and encephalitis. A) Frontal cortex with cortical thinning (double-headed arrow) and vacuolation (arrows) (Luxol fast blue stain with periodic acid–Schiff method [LFB/PAS], original magnification ×10). B) Frontal cortex with vacuolation (arrow) and rare residual neurons (arrowheads) (LFB/PAS, original magnification ×50). C) Marked astrogliosis in the frontal cortex (glial fibrillary acidic protein [GFAP] immunostain, original magnification ×100). D) White matter with marked astrogliosis (GFAP immunostain, original magnification ×100). E) Penetrating artery with abundant CD3+ T-cells in the perivascular space and adjacent brain parenchyma (CD3+ immunostain, original magnification ×25). F) CD3+ T-cells as part of microglial nodules (CD3+ immunostain, original magnification ×100). G) White matter in the internal capsule showing myelin clumps (arrowheads) and vacuolation (arrow) (LFB/PAS, original magnification ×100). H) Loss of axons in the internal capsule (Bielschowsky nerve fiber silver stain, original magnification ×100). I) Internal capsule with marked microgliosis (CD68+ immunostain, original magnification ×40). J) Microcalcifications (arrow) in the globus pallidus (LFB/PAS, original magnification ×100). All paraffin sections were counterstained with hematoxylin.