Glycogen storage disease due to phosphoglucomutase deficiency

Glycogen storage disease due to phosphoglucomutase deficiency, also known as GSD type XIV or PGM1-CDG (PGM1-congenital disorder of glycosylation), is a rare inherited metabolic disorder caused by mutations in the PGM1 gene. Phosphoglucomutase 1 (PGM1) is an enzyme that plays a critical role in both glycogen metabolism and protein glycosylation, catalyzing the interconversion of glucose-1-phosphate and glucose-6-phosphate. Because of this dual role, the condition is now more commonly classified as a congenital disorder of glycosylation (CDG) rather than purely a glycogen storage disease. The disease affects multiple body systems. Key clinical features include exercise intolerance, muscle weakness, and episodes of rhabdomyolysis. Patients frequently present with a bifid uvula or cleft palate, short stature, and hepatopathy with elevated liver transaminases. Dilated cardiomyopathy is a serious complication that can develop over time. Endocrine abnormalities such as hypogonadotropic hypogonadism and growth hormone deficiency have been reported. Coagulation abnormalities and hypoglycemia (particularly fasting hypoglycemia) are also characteristic. Laboratory findings typically show abnormal transferrin isoelectric focusing patterns consistent with a CDG, along with low serum levels of various glycoproteins. Treatment is primarily supportive and symptomatic. Oral D-galactose supplementation has shown promise in improving glycosylation abnormalities in affected patients and is considered a targeted dietary therapy. Management also includes avoidance of fasting, dietary modifications to prevent hypoglycemia, physical therapy for muscle weakness, and cardiac monitoring for cardiomyopathy. Multidisciplinary care involving metabolic specialists, cardiologists, endocrinologists, and geneticists is recommended.

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