Fatigue induced in the TA muscle following a high number of stimulations together with a pronounced deficit in force produced by the diaphragm muscle from Gfpt1tm1d/tm1d mice, is indicative of a myopathy, and consistent with EMG recordings in patients with mutations in GFPT1 as well as other genes in the glycosylation pathway including ALG2, ALG14, DPAGT1 and GMPPB (1,2,4–9,12,23). Here, GFPT1 is linked to myopathy.