The critical role of histology in distinguishing sarcoidosis from common variable immunodeficiency disorder (CVID) in a patient with hypogammaglobulinemia.

Background: Common variable immunodeficiency disorders (CVID) are a rare group of primary immune defects, where the underlying cause is unknown. Approximately 10-20% of patients with typical CVID have a granulomatous variant, which has closely overlapping features with sarcoidosis.

Case Presentation: Here we describe a young man who sequentially developed refractory Evans syndrome, cauda equina syndrome and most recently renal impairment. Following immunosuppression, he has made a recovery from all three life-threatening autoimmune disorders. As the patient was hypogammaglobulinemic for most of the time while on immunosuppression, vaccine challenges and other tests were not possible. Histological features were in keeping with sarcoidosis rather than the granulomatous variant of CVID. In the brief period when immunosuppression was lifted between the cauda equina syndrome and renal impairment, he normalised his immunoglobulins, confirming sarcoidosis rather than CVID was the underlying cause.

Conclusion: We discuss diagnostic difficulties distinguishing the two conditions, and the value of histological features in our diagnostic criteria for CVID in identifying sarcoidosis, while the patient was hypogammaglobulinemic. The key message from this case report is that the characteristic histological features of CVID can be very helpful in making (or excluding) the diagnosis, particularly when other tests are not possible.