Department of Clinical Immunology Department of Infectious Diseases, Rigshospitalet, University of Copenhagen Department of Infectious Diseases, Odense University Hospital, University of Southern Denmark, Odense International Reference Laboratory of Mycobacteriology, Statens Serum Institut, Copenhagen, Denmark Department of Internal Medicine, Landssjúkrahúsið, Tórshavn, the Faroe Islands.
Interleukin-12 receptor deficiency is a well-described cause of human susceptibility to infection with low-virulent mycobacteria and Salmonella species. We identified a male patient presenting in his late forties with severe gastro-enteropathy due to outbred infestation by a previously unknown mycobacterium. In addition to selective IgA deficiency, the patient was found to carry a not previously described R283X homozygous mutation in his IL12R?1 gene. Two of his sisters, a brother, and his four children were healthy, heterozygous carriers of the mutation. In this patient, the combination of two deficiencies could promote illness: Even though the IgA deficiency in itself does not predispose to mycobacterial disease, the lack of secreted IgA may have disturbed the intestinal homeostasis and increased the susceptibility l to the low-virulent mycobacterium that the patient was not able to clear due to his IL12R deficiency. Antimycobacterial chemotherapy and interferon-? treatment for two years significantly improved his condition. This is the first description of IL12R?1 deficiency combined with another immunodeficiency, and we suggest that combinatory defects may circumvent the otherwise low penetrance of IL12RB1 deficiency.