[Disseminated BCG infection revealing X-linked severe combined immunodeficiency]

Live attenuated Bacillus Calmette-Guérin (BCG) vaccine is rarely responsible for disseminated infection. We report a case of X-linked severe combined immunodeficiency (SCID) revealed by a disseminated skin infection.

A 4-month-old baby was hospitalized for prolonged gastroenteritis. He was in poor general condition, with prolonged fever, oral and gluteal candidiasis and purple nodules associated with ulceration of the BCG scar. The absence of a thymus, T-cells and NK-cells, and the presence of nonfunctional B-lymphocytes led to a diagnosis of SCID. Biopsies of nodules revealed a dermal infiltrate without necrosis. A Ziehl-Neelson stain was highly positive and the culture grew Mycobacterium bovis. Treatment consisted of a four-drug antibiotic regimen directed against M. bovis combined with gamma interferon, immunoglobulins and antibiotic prophylaxis by cotrimoxazole and was followed by a haploid-identical bone marrow transplant without rejection at six months. The early death of the child's maternal uncle from sepsis suggested X-linked transmission, which was subsequently confirmed by genetic analysis.

BCG vaccination can cause serious infections in immunocompromised subjects. Skin involvement is extremely rare but may be the first sign of SCID, of which the X-linked form is the most common and corresponds to a variety of mutations in the gene coding for the gamma chain common to several interleukin receptors. Genetic counselling is essential to identify female carriers and allow early antenatal diagnosis. Bone marrow transplantation is the only treatment.