A 7-month-old boy presented with left axillary lymphadenopathy persisting for two to three weeks. His past medical history was unremarkable with the exception of recurrent oral candidiasis. His parents were first-degree relatives. Family history was negative for genetic disorders or tuberculosis. He was vaccinated with BCG at the age of three months. On admission, routine physical examination was unremarkable with the exception of lymphadenopathy with a diameter of 5x5 cm in the left axillary region. There was a BCG vaccine scar on his left shoulder.
The tuberculin skin test was positive (15x15 mm). Thoracic computed tomography and abdominal ultrasonography were normal. The lymph node biopsy was performed and pathohistological examination showed a widespread infiltration of lymphohistiocytes. A few small granulomas without caseous necrosis were present. Ziehl Neelsen stain for acid-fast bacilli showed the presence of multibacillar histiocytes. M. tuberculosis complex PCR and culture were negative. Routine immunological evaluation including serum IgG, IgA, IgM, IgE, peripheral blood lymphocyte subsets and phagocyte respiratory burst assay were normal. Whole blood samples were in vitro activated with BCG, BCG plus IL-12 and BCG plus IFN-gamma as described previously. IL12p40 production was increased after stimulation with BCG plus IFN-gamma (Figure, a). In contrast, IFN-gamma production to BCG plus IL-12 was blunted (Figure, b). IL-12Rbeta1 molecule expression on activated T cells was found to be negative by flow cytometric analysis (data not shown). DNA sequencing of the IL12RB1 gene revealed a new homozygous mutation (64+1G>T). The patient's parents and brother were heterozgyous for this mutation and healthy. So, following the genetic analysis, the healthy brother was vaccinated with BCG at the age of three months.
The patient was treated with isoniazide (INH), rifampicin (RIF) and ethambutol for the first two months and then treatment continued with INH and RIF for another six months. Drainage of purulent material from the operation wound discontinued at the fourth month of the treatment. Eight months passed since the end of treatment and he is doing well with the exception of oral candidiasis.