Benign course of glycogen storage disease type IIb in two brothers: Nature or nurture?

Two brothers with the childhood variant of type II glycogenosis (GSD‐IIb) treated with nutrition and exercise therapy (NET) from a young age showed an unusually benign course. Muscle biopsy from the older brother, which showed characteristic vacuolar glycogen accumulation at age 2, had reverted to normal by age 16. A muscle biopsy from the younger brother was normal at 5 years. It is uncertain whether this anomalous evolution was spontaneous (nature) or due to the symptomatic therapy (nurture), but NET should be considered in patients with GSD‐IIb until enzyme replacement or gene therapy become generally available. Muscle Nerve, 2005