Chronic recurrent multifocal osteomyelitis preceding pyoderma gangrenosum and occult ulcerative colitis in a pediatric patient.

Chronic recurrent multifocal osteomyelitis (CRMO) is a clinicopathologic entity of unknown origin mainly affecting children and young adults. It shares many clinical features with pyoderma gangrenosum (PG), an uncommon ulcerating inflammatory disorder of the dermis and underlying subcutaneous fat. Both conditions are chronic and relapsing, and have been associated with inflammatory bowel disease (IBD). The diagnoses are made by exclusion. Histology is nonspecific and cultures are negative. There has been only one previous report of both conditions occurring in the same patient. Here we describe the second case, a 12-year-old girl who developed pyoderma gangrenosum in direct continuity to an underlying CRMO lesion of the right anterior tibia. Occult ulcerative colitis (UC) was subsequently discovered.