Antacid-induced hypophosphatemia: an unusual cause of "pseudo-myopathy".

A 69 year old man presented with painful proximal muscle weakness which clinically simulated polymyositis. Further evaluation revealed normal muscle enzymes and hypophosphatemia which resulted from unsuspected antacid abuse. "Pseudo-myopathy" is one example of the myriad of rheumatic diseases which may be mimicked by hypophosphatemia.