Neutropenia and recurrent infections are common manifestations of glycogen storage disease 1b (GSD1b), a disease caused by mutations in G6PT1, the glucose 6 phosphate transporter 1 gene. Patients with GSD1b have complex defects in neutrophil deployment and function. GSD1b causes recurrent infections – gingivitis, mouth ulcers, respiratory infections, abscesses and enterocolitis. Granulocyte colony-stimulating factor (G-CSF) has been used to treat these patients for more than 2 decades.
We reviewed the presentations, manifestations, complications and G-CSF treatment for 54 GSD1b patients (31 adults and 23 children) at Duke University, the University of Florida and through the Severe Chronic Neutropenia International Registry at the University of Washington. Observational data were available on most patients for at least 3 years (mean = 12 years, median = 13 years, range = 1 to 23 years). Available data showed that before treatment with G-CSF, all of these patients had mild to moderate neutropenia; the mean of the median absolute neutrophil count (ANC) was 0.839 × 109/L ± 0.165 SEM (median = 0.503 × 109/L, range = 0.038 to 7.665 × 109/L). All of the patients also had recurrent infections; the most common events were mouth ulcers, otitis and skin abscesses. There were 7 patients who had enterocolitis prior to G-CSF treatment.
G-CSF therapy was initiated at various ages ranging from birth to age 30 (mean = 6 years, median = 4 years). Initial daily doses of G-CSF ranged from 0.50 to 63.28 mcg/kg/day (mean = 5.86, median = 3.65) and were generally titrated upward to achieve a normal neutrophil count. The mean ANC on treatment was 2.598 × 109/L ± 0.136 SEM (median = 1.856 × 109/L, range = 0.0 to 12.645 × 109/L). G-CSF treatment was uniformly associated with an increase in blood neutrophils and reduced patterns of infection. In most patients the symptoms of enterocolitis improved within a few days to a few weeks after starting G-CSF therapy. An increase in spleen size also commonly occurred. In 630 patient-years of observation, there have been 3 deaths attributable to the following causes: 1 subject died of sepsis, 1 subject died of complications from hepatomegaly and neutropenia, and 1 subject died 6 years after a liver transplant. The subject developed AML 5 years after the liver transplant while receiving a combination of immunosuppressant drugs.
Patients with GSD1b associated neutropenia respond well to G-CSF with reduced infections and symptoms of enterocolitis. Long-term complications are infrequent and G-CSF is well tolerated in most patients.
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Asterisk with author names denotes non-ASH members.