Disseminated bacillus Calmette-Guérin infections in patients with primary immunodeficiencies

The pathologic findings from biopsy or autopsy material in four patients, who were vaccinated with bacillus Calmette-Guérin (BCG) at birth in Chile, are presented. Two patients had severe combined immunodeficiency, and two had more restricted cellular (T-cell) immunodeficiency with no evidence of human immunodeficiency virus infection. The patients had distinct skin nodules and nodular lesions in systemic organs and bone marrow. Three patients had regional BCG lymphadenitis. One patient with severe combined immunodeficiency, however, had disseminated BCG without any local reaction. In all cases BCG strains of Mycobacterium were identified in a reference mycobacteriology laboratory. The histologic lesions in most patients usually consisted of diffuse histiocytic infiltrates with poorly formed granulomas and variable or no necrosis. Histiocytes were plump and engorged with numerous acid-fast bacilli (AFB). In some areas the massive histiocytosis resembled a spindle cell neoplasm. Other histologic findings supported the underlying immunodeficiency. The pattern of histiocytic response and degree of microbial killing depend on the host's immunocompetence. In the later stages of disease or in severe immunodeficiency, there is a lack of granuloma formation and unimpeded proliferation of AFB. These findings are reminiscent of nontuberculous mycobacterial infections in AIDS patients. Bacillus Calmette-Guèrin dissemination has to be considered in immunocompromised individuals when the patient comes from other countries in which such vaccinations are practiced.