Abstract
Ten patients in whom the clinical findings were consistent with the syndrome variously described as 'benign myalgic encephalomyelitis', 'epidemic neuromyasthenia', 'Royal Free disease' and 'Icelandic disease' were investigated for blood levels of myoglobin and various enzymes. Although there is no clinical resemblance between the two diseases, the biochemical pattern bears a close similarity to that found in Duchenne muscular dystrophy (DMD) though differing sharply in that no rise in creatinine kinase levels was found. These findings are discussed with particular reference to recent suggestions that the permeability of cell membranes may be impaired by changes in intracellular energy mechanisms.