LAUSR

To the Editor Mendelian susceptibility to mycobacterial diseases (MSMD) is a group of rare primary immunodeficiency (PID) diseases characterized by defects of IL-12/IFN-γ pathway. The defect predisposes an individual for infections with unusual intracellular organisms typically mycobacteria and salmonella [1, 2]. Autoimmune manifestations only rarely develop in these patients [3–8]. We report one such patient with IL-12 receptor β1 defect who had recurrent Salmonella typhi infection, leukocytoclastic vasculitis, and autoimmune hemolytic anemia. Index boy was symptomatic since the age of 1 month. He was being treated at a local health care facility before referral. At 1 month of age, he was diagnosed to have Bacillus Calmette–Guérin (BCG) lymphadenitis. He also had recurrent episodes of dysentery, oral thrush, and purulent ear discharge. At 6 years of age, he started developing multiple pus discharging sinuses in the right leg and forearm. This was managed as tubercular osteomyelitis but no organism was isolated at this time. This treatment led to the healing of the sinuses and formation of scars. He was born out of a nonconsanguineous marriage in India with no suggestive family history of recurrent infections or autoimmunity. He presented to us at 10 years of age with diarrhea and fever for 20 days. On examination, he had pallor, multiple healed scars over the right leg, right dorsum of the foot and right forearm (Fig. 1a), and hepatomegaly. The rest of the examination was unremarkable. A clinical possibility of PID was considered. Laboratory investigations showed hemoglobin 64 g/l, white blood cell count 14.2 × 10 cells/L (Polymorphs83%/ Lymphocytes10%/Monocytes7%), absolute lymphocyte counts 1.42 × 10 cells/L, platelet counts 424 × 10/L, C-reactive protein 106 g/l (N < 6), and erythrocyte sedimentation rate 64mm in the first hour. Stool culture and blood culture grew Salmonella typhi (sensitive to ceftriaxone). Blood and stool culture did not grow any mycobacteria. Immunological investigations are summarized in Supplementary Table 1. The flow cytometric expression of IL-12Rβ1 on stimulated lymphocytes was markedly reduced as compared to control. Molecular analysis confirmed a previously described homozygous nonsense mutation in the IL-12RB1 gene (c.962C > A, p.S321*). Mother, father, and younger brother were found