Rheumatoid‐nodule‐like cutaneous granuloma associated with recombinase activating gene 1‐deficient severe combined immunodeficiency: A rare case

Cutaneous granulomas without detectable infectious etiology rarely occur in children and adults with primary immunodeficiency disorders. These cutaneous granulomas are primarily seen in combined variable immunodeficiency, ataxia‐telangiectasia, and severe combined immunodeficiency (SCID) and can emulate the reaction patterns seen in sarcoidosis and granuloma annulare. To date, the literature has described only six cases of non‐infectious cutaneous granulomas in SCID. We report an unusual case of cutaneous granuloma, mimicking a sarcoma, in a 40‐year old male with recombinase activating gene 1‐deficient SCID, who presented with a slow‐growing globus mass over the lateral aspect of the right elbow. There was heterogeneous enhancement on MRI, which was concerning for neoplasm but no malignancy was found on frozen or permanent sections. GMS, PAS with diastase, and AFB stains, as well as microbiology cultures, were negative. An AE1/AE3 stain was negative and a CD163 stain highlighted histiocytes. No infectious etiology was identified and histopathology revealed palisaded granulomatous dermatitis, most closely resembling a rheumatoid nodule. Although cutaneous manifestations have been reported in nearly half of primary immunodeficiency disorder cases, non‐infectious cutaneous granulomas are exceedingly rare in SCID. To our knowledge, this is the first case report of cutaneous palisaded granulomatous dermatitis mimicking a rheumatoid nodule in a major joint.