Diagnosis and follow-up of glycogen storage disease (GSD) type VI from the largest GSD center in China

Glycogen storage disease (GSD) Type VI is a glycogenolysis disorder caused by variants of PYGL. Knowledge about this disease is limited because only approximately 50 cases have been reported. We investigated the clinical profiles, molecular diagnosis, and treatment outcomes in patients with GSD VI from 2000 to 2021. The main initial clinical features of this cohort include hepatomegaly, short stature, elevated liver transaminases, hypertriglyceridemia, fasting hypoglycemia, and hyperuricemia. After uncooked cornstarch treatment, the stature and biochemical parameters improved significantly (p < 0.05). However, hyperuricemia recurred in most patients during adolescence. Among the 56 GSD VI patients, 54 biallelic variants and two single allelic variants of PYGL were identified, of which 43 were novel. There were two hotspot variants, c.1621-258_2178-23del and c.2467C>T p.(Gln823*), mainly in patients from Southwest and South China. c.1621-258_2178-23del is a 3.6 kb deletion that results in an out-of-frame deletion r.1621_2177del and an in-frame deletion r.1621_2265del. Our data show for the first time that long-term monitoring of uric acid is recommended for older GSD VI patients. This study also broadens the variant spectrum of PYGL and indicates that there are two hot-spot variants in China.