Neonatal onset multisystem inflammatory disease (NOMID), an autoinflammatory disease, is characterized by fever, chronic urticarial rash, CNS manifestations, and arthropathy. Approximately 50% of patients with NOMID have de novo missense mutations in CIAS1, which is associated with modulation of the IL-1b and apoptotic pathways. Approximately 60% of NOMID patients have prominent arthropathy, most commonly involving the knees, the cause of which remains poorly understood.

To more fully describe the findings of NOMID arthropathy on MRI and radiography and to provide a better understanding of the origin of the bony lesions.

We imaged 20 patients with NOMID to further investigate NOMID-associated bony lesions.

Bony abnormalities were seen in the knees of 11/20 patients. The knee findings included enlarged, deformed femora and patellae in all and tibiae in the majority, without evidence of synovitis. Some patients had other joint involvement. Most had short stature and valgus or varus knee deformities. No association was noted between bony abnormalities and CIAS1 mutations. The abnormalities appeared to be the result of a mass-producing process. The resulting heterogeneously calcified masses appeared to originate in the physis and deformed the adjacent metaphysis and epiphysis.

These findings suggest that the arthropathy of NOMID is the result of abnormal endochondral bone growth. Further investigation is needed to determine whether this deformity is triggered by inflammation early in development or by CIAS1 mutations causing abnormal chondrocyte apoptosis.