Disseminated Bacillus Calmette-Guérin Osteomyelitis in Twin Sisters Related to STAT1 Gene Deficiency.

Mendelian susceptibility to mycobacterial disease is a rare syndrome characterized by severe clinical infections usually caused by weakly virulent mycobacterial species such as Bacillus Calmette-Guérin vaccines and environmental nontuberculous mycobacteria or more virulent mycobacteria as mycobacterium tuberculosis. Since 1996, 9 genes including 7 autosomal ( STAT1, IFNGR1, IFNGR2, IL12B, IL12RB1, ISG15, and IRF8) and 2 X-linked genes ( NEMO and CYBB) have been identified. Allelic heterogeneity leaded to recognize about 18 genetic diseases with variable clinical phenotypes, but sharing a same physiological mechanism represented by a defect in human IL-12-dependant-INF-γ-mediated immunity. We report here a case of multifocal Bacillus Calmette-Guérin osteomyelitis in a context Mendelian susceptibility to mycobacterial disease mimicking a metastatic neuroblastoma in a child presenting with delayed growth. The investigation of her twin sister showed the same disease. A heterozygous mutation in exon 22 of STAT1 gene was found in both sisters, another sister and the father being healthy and heterozygous for the same mutation.