Learning Points TAP1 deficiency is a rare autosomal recessive immunodeficiency characterized by defective MHC class I expression and reduced CD8+ T cell function. Clinical features such as granulomatous skin lesions, palatal perforation, and saddle‐nose deformity may mimic autoimmune vasculitides (e.g., granulomatosis with polyangiitis), leading to potential misdiagnosis. The combination of ANCA negativity, early‐onset symptoms, and strong familial clustering in patients with granulomatous disease should raise suspicion of an underlying primary immunodeficiency.
Akay et al. (Sun,) studied this question.