Background: Non-infective cutaneous granulomas with unknown pathogenesis occur in various primary immunodeficiencies (PIDs) including ataxia telangiectasia (A-T). Objective: To find a common immunological denominator in these cutaneous granulomas. Methods: The dermatological and immunological features of 4 patients with A-T and cutaneous granulomas were described. The literature on skin granulomas in A-T and in other PIDs is reviewed. Results: All 4 A-T patients had progressive granulomas on their limbs and showed decreased IgG and IgA concentrations with normal IgM levels. They had a marked decrease in B cells and naïve T cells coinciding with the appearance of the cutaneous granulomas. Similar B- and T-cell abnormalities were described in patients with other PIDs with skin granulomas. Conclusions: We hypothesize that the pathogenesis of these skin granulomas is related to immune dysregulation of macrophages due to the absence of naïve T cells with an appropriate T-cell receptor repertoire and the unopposed activity of γδ T cells and/or natural killer cells.

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