No abstract

The immunogenetic basis of severe infections caused by bacille Calmette-Guérin vaccine and environmental mycobacteria in humans remains largely unknown. We describe 18 patients from several generations of 12 unrelated families who were heterozygous for 1 to 5 overlapping IFNGR1 frameshift small deletions and a wild-type IFNGR1 allele. There were 12 independent mutation events at a single mutation site, defining a small deletion hotspot. Neighbouring sequence analysis favours a small deletion model of slipped mispairing events during replication. The mutant alleles encode cell-surface IFNgamma receptors that lack the intra-cytoplasmic domain, which, through a combination of impaired recycling, abrogated signalling and normal binding to IFNgamma exert a dominant-negative effect. We thus report a hotspot for human IFNGR1 small deletions that confer dominant susceptibility to infections caused by poorly virulent mycobacteria.

Chronic granulomatous disease (CGD) is an inherited disorder characterized by the inability of phagocytes to generate normal amounts of superoxide (O2-), leaving patients susceptible to life-threatening infections. It was previously assumed that once carriers of the X-linked form of CGD were found to have 30% or more of functionally normal neutrophils, they would be free of risk for infection because the lyonization ratio was believed to be constant. Our report strongly contradicts this assumption. A 45-year-old X-CGD carrier had approximately 40% of normal neutrophils in her peripheral blood at age 21 years. Recently, she contracted a life-threatening pulmonary infection with Aspergillus fumigatus. After recovery, the ratio of normal-to-nonfunctional neutrophils was re-evaluated. She was found to have only 6-8% of normal neutrophils, suggesting that a striking decrease in the number of normal cells over the past 25 years was the reason for an increased susceptibility to Aspergillus infection. We conclude that age-related acquired skewing of the lyonization ratio can result in an increased susceptibility to life-threatening infections in X-CGD carriers.

Glycogen storage disease type Ib has all the clinical manifestations of glycogen storage disease type Ia such as hepatomegaly, growth retardation, bleeding tendency, hypoglycemia, hyperlactacidemia, hyperuricemia, hyperlipidemia, impaired platelet function plus neutropenia. The overall glucose-6-phosphatase activity in disrupted microsomes from liver is normal whereas glucose-6-phosphate translocase, the first enzyme in the glucose-6-phosphate transport system is absent. There is no glucose-6-phosphatase activity in vivo. Recent results show that in granulocytes the glucose-6-phosphate-dependent hexosemonophosphate-shunt is impaired.