TAP-I Deficiency Presenting With Chronic Granulomatous Rubella Virus-Driven Cutaneous Ulceration: A Case Report and Scoping Literature Review.

Autosomal recessive mutations in TAP1, TAP2, TAPBP, or B2M, are associated with major histocompatibility complex (MHC) class I deficiency. Individuals may present with granulomatous skin ulceration, but the underlying antigenic triggers remain largely unknown. We identified TAP1 deficiency in a 32-year-old female referred with a 7-year history of localized skin ulceration. Histologic immunofluorescence revealed that rubella virus (RuV) infection was a likely driver of the associated inflammation, and modest clinical improvement was observed following topical calcineurin inhibition. To better define the natural history, clinical, and immunological manifestations of this condition, we also performed a scoping literature review. We identified 45 unique individuals from 36 reports with a combined follow-up duration of 1,184 patient years. Chronic necrotizing granulomatous skin lesions and childhood-onset bronchiectasis were common. Five deaths were reported (median age 36 years), typically linked to respiratory complications. Phenotypic heterogeneity was evident, with at least four individuals reaching adulthood without clinical symptoms. Diagnostic delay frequently exceeded a decade amongst symptomatic individuals, with misdiagnosis of granulomatous disease prompting systemic immunosuppression and infection-related morbidity. The presence of an abnormal CD8+ T-cell count or a history of consanguinity offered low sensitivity for MHC I deficiency (~ 50%), indicating a low threshold for further investigation is required for correct diagnosis. Graphical review of case reports identified morphologically similar lesions in other MHC I-deficient individuals. These findings suggest that the phenomenon of MHC I deficiency is underreported and that diagnosis should prompt testing for RuV.