Caseous Granuloma: Tuberculosis or Chronic Recurrent Multifocal Osteomyelitis?

Background: chronic recurrent multifocal osteomyelitis (cremo) is one of the autoinflammatory bone disorders due to disturbance in innate immune system. up to now, there is no reported case of caseous granulomas in the cremo. we report a boy with sterile granolumatous osteomyelitis. case presentation: a four-year-old boy presented with swelling and pain in the left wrist, malaise and bilateral erythematous pustulosis on the palmar region which had resolved spontaneously after about 7 days. the histopathology of the lesions showed severe acute and chronic inflammatory process and chronic granulomatous reaction with caseating necrosis (granulomatous osteomyelitis). the direct smear, culture and pcr for the mycobacterium tuberculosis and atypical mycobacteria were negative. about five months after initiation of the anti-mycobacterial treatment, he was referred to the rheumatology clinic with left elbow pain, effusion and decreased range of motion, and bilateral erythematous palmar pustulosis. he was diagnosed as cremo based on two exacerbations, repeatedly negative cultures, and concomitant acute and chronic lesions in the histopathology and x-ray. naproxen and pamidronate every 3 months were started and all other medications were stopped. two months after the first dose of pamidronate, he became symptom-free and forearm x-ray showed disappearance of the osteolytic lesions and periosteal reactions. conclusion: the diagnosis of cremo should be considered in the patients with lytic bone lesions. in addition, the clinicians should be aware of the possibility of caseating granuloma in the cases with possible diagnosis of cremo.