• muscle
• metabolism
• neuromuscular
• diagnosis

In a recent paper published in the Journal of Clinical Pathology,1 we raised the clinical significance of hyperammonaemia after the non-ischaemic forearm exercise test (NIFET) in detecting various glycogen storage diseases (GSD). The results of this work revealed that hyperammonaemia may occur in several GSD. In absence of lactate rise (less than 0.8 mmol/L), severe hyperammonaemia (defined as a rise of more than 141 µmol/L) is generally a hallmark of myophosphorylase deficiency (McArdle disease).2 In the presence of lactate rise (more than 0.8 mmol/L), hyperammonaemia was observed in deficiency in debranching enzyme, in phosphorylase b-kinase and in phosphoglucomutase 1. We would like to add another GSD to the list of possible diagnoses: phosphoglycerate kinase 1 (PGK1) deficiency.

A man diagnosed in 1979 with a PGK1 deficiency recently underwent the …