BCG osteomyelitis: tips for diagnosis

Objective: To report the clinical and imaging characteristics of BCG-osteomyelitis, and compare them with those of pyogenic osteomyelitis. Materials and methods: Clinical and imaging findings were retrospectively evaluated in 14 children with BCG osteomyelitis, including 3 with Mendelian susceptibility to mycobacterial diseases (MSMD), and in 40 children with pyogenic osteomyelitis, using Fisher exact and Mann-Whitney U tests. Results: BCG-osteomyelitis was an indolent inflammatory disease of young children (mean age 15.5 months). Immunocompetent patients came to medical attention over months after vaccination, while patients with MSMD much earlier (the average time lapse: 13.7 vs. 5.0 months). The former manifested with a slowly progressive, painless mass with only mildly increased acute-phase reactants, while the latter started with lymphadenitis with significant inflammatory reactions and later developed osteomyelitis. These clinical scenarios contrasted with acute febrile illness in pyogenic osteomyelitis. The imaging findings were identical in both immunocompetent and MSMD groups; however, the former showed monoostotic involvement, while the latter polyostotic affliction. The typical imaging finding of BCG-osteomyelitis comprises a large intraosseous abscess with modest reactive edema commonly associated with transphyseal extension from the metaphysis to the epiphysis, contrasting with the manifestation of pyogenic osteomyelitis; size of abscess (p=0.028), pattern of abscess extension (p<0.001), and extent of surrounding edema (p<0.001). Conclusions: BCG-osteomyelitis should be suspected in children under 2 years of age with insidious osteomyelitis, accompanied with characteristic imaging findings. Polyostotic BCG osteomyelitis is highly suggestive of MSMD. Awareness of the distinctive features of BCG-osteomyelitis enables the early diagnosis and timely therapeutic intervention.