Granulomatous inflammation: The overlap of immune deficiency and inflammation.

Pediatric granulomatous diseases constitute a heterogenous group of conditions in terms of clinical phenotypes, pathogenic mechanisms, and outcomes. The common link is the presence of multinucleated giant cells in the inflammatory infiltrate. The clinical scenario in which a tissue biopsy shows granulomatous inflammation is not an uncommon one for practicing adult and pediatric rheumatologists. Our role as rheumatologists is to develop a diagnostic plan based on a rational differential diagnostic exercise tailored to the individual patient and based mainly on a detailed clinical assessment. This chapter presents a comprehensive differential diagnosis associated with a classification developed by the authors. We describe with some detail extrapulmonary sarcoidosis, Blau syndrome, and immunodeficiency associated granulomatous inflammation, which in our view are the paradigmatic primary forms of granulomatous diseases in childhood. The other entities are presented only as differential diagnoses listing their most relevant clinical features. This chapter shows that almost all granulomatous diseases seen in adults can be found in children and that there are some entities that are essentially pediatric at onset, namely Blau syndrome and most forms of immunodeficiency associated granulomatous diseases.