Hyperimmunoglobulinemia D Syndrome Masquerading as Familial Mediterranean Fever, Hidradenitis Suppurativa, and Crohn's Disease: A Case Report.

We report a rare case of hyperimmunoglobulinemia D syndrome (HIDS) in a young man who was initially diagnosed with familial Mediterranean fever, hidradenitis suppurativa, and, eventually, with Crohn's disease. The final diagnosis of HIDS was based on whole-exome sequencing. The unique concurrence of these three conditions has not been reported previously. The multiple diagnoses and overlapping presentations of these conditions should raise awareness about alternative diagnoses that mimic inflammatory and autoimmune conditions, including HIDS, a rare but clinically relevant condition. Exploring patients' family histories to understand the genetic contribution to HIDS is also important. This is evidenced by the fact that whole-exome sequencing for our patient was performed because the patient's brother was diagnosed with HIDS, and the sequencing led to the final diagnosis.