Use the forearm exercise test findings in lipid metabolic myopathy, Pompe disease, and Cori–Forbes disease to frame the working diagnosis and next step; let it shape prognosis counseling and follow-up intensity. Make Pompe disease the checkpoint that determines whether you escalate testing, narrow the differential, or change treatment.

Pompe disease can present from infancy through adulthood; Adult-onset Pompe often causes proximal weakness with respiratory involvement and a normal CK; Dried blood spot acid alpha-glucosidase testing is now the preferred screen; Cori-Forbes disease can combine distal and proximal weakness with liver, heart, and respiratory involvement; A reversed forearm exercise pattern points more toward lipid metabolic myopathy than glycogen storage disease