Blurring the lines in interferon {gamma} receptor deficiency: an infant with near-fatal airway disease.

Deficiencies of the interferon γ (IFN-γ) pathway have become a well-recognized cause of nontuberculous mycobacterial infection. We report here a case of autosomal dominant IFN-γ receptor 1 (IFN-γ-R1) deficiency presenting at the unusually young age of 16 months with a severe clinical course. Mycobacterium avium complex was cultured from bronchial washings of a child who presented with primary endobronchial disease after a 4-month history of rhinorrhea, wheeze, and acute lobar consolidation. A maternal history of multifocal Mycobacterium kansasii osteomyelitis and cutaneous M avium complex led to genetic confirmation of IFN-γ-R1 818del4 deletion (a 4 base pair deletion at nucleotide position 818) in both family members. This case demonstrates the link between mycobacterial disease and IFN-γ pathway deficiency, the diagnosis of which facilitates more accurate therapy and genetic counseling. The case also raises questions about the reported distinct presentation, treatment, and prognosis of autosomal dominant and recessive IFN-γ-R1 phenotypes.