Autosomal Recessive IL-12p40 Deficiency due to a Mutation in the Gene: Report of a Brazilian Patient with Lymph Node Mycobacterial Infection.

Autosomal recessive interleukin (IL)-12p40 deficiency is a genetic etiology of Mendelian susceptibility to mycobacterial disease (MSMD). It has been described in ∼50 patients, usually with onset at childhood with Bacille Calmette-Guérin (BCG) and infections. A male patient born to consanguineous parents was diagnosed with presumed lymph node MSMD at the age of 13 years after ocular symptoms. A positive history of inborn error of immunity was present: BCG reaction, skin abscess, and recurrent oral candidiasis. Abnormal measurements of cytokine levels, IL-12p40 and interferon-gamma (IFN-γ), lead to the diagnosis of MSMD. Genetic analysis showed a mutation in exon 7 of the gene. Currently, the patient is alive under prophylactic antibiotics. We report a rare case of IL-12p40 deficiency in a Latin American patient. Medical history was crucial for immune defect suspicion, as confirmed by precision diagnostic medicine tools.