Interferon γ receptor 1 (IFNγ R1) deficiency is a primary immunodeficiency with allelic dominant and recessive mutations characterised clinically by severe infections with mycobacteria. We aimed to compare the clinical features of recessive and dominant IFNγR1 deficiencies.

We obtained data from a large cohort of patients worldwide. We assessed these people by medical histories, records, and genetic and immunological studies. Data were abstracted onto a standard form.

We identified 22 patients with recessive complete IFNγR1 deficiency and 38 with dominant partial deficiency. BCG and environmental mycobacteria were the most frequent pathogens. In recessive patients, 17 (77%) had environmental mycobacterial disease and all nine BCG-vaccinated patients had BCG disease. In dominant patients, 30 (79%) had environmental mycobacterial disease and 11 (73%) of 15 BCG-vaccinated patients had BCG disease. Compared with dominant patients, those with recessive deficiency were younger at onset of first environmental mycobacterial disease (mean 3·1 years [SD 2·5] vs 13·4 years [14·3], p=0·001), had more mycobacterial disease episodes (19 vs 8 per 100 person-years of observation, p=0·0001), had more severe mycobacterial disease (mean number of organs infected by Mycobacterium avium complex 4·1 [SD 0·8] vs 2·0 [1·1], p=0·004), had shorter mean disease-free intervals (1·6 years [SD 1·4] vs 7·2 years [7·6], p<0·0001), and lower Kaplan-Meier survival probability (p<0·0001). M avium complex osteomyelitis was more frequent in dominant than in recessive patients (22/28 [79%] vs 1/8 [13%], p=0·002), and this disorder without other organ involvement arose only in dominant patients (9/28 [32%]). Disease caused by rapidly growing mycobacteria was present in more recessive than dominant patients (7/22 [32%] vs 1/38 [3%], p=0·002).

Recessive complete and dominant partial IFNγR1 deficiencies have related clinical phenotypes, but are distinguishable by age at onset, dissemination, and clinical course of mycobacterial diseases. A strong correlation exists between IFNGR genotype, cellular responsiveness to interferon γ, and clinical disease features.