[Muscle biopsy studies in malignant hyperthermia].

Muscle biopsies were carried out in 41 patients with malignant hyperthermia, or supposed at-risk, as well as in some of their relatives. In 20 patients no changes were detected, and in 2 patients only acute rhabdomyolysis was seen (53.7%); in 19 patients (that is 46.3%) myopathic aspects were found in form of minimal changes, but also of syndrome-like tissue alterations (e.g. core disease, muscle dystrophy). These results confirm the existence of a morphologically detectable "subclinical myopathy" in about half of our patients. Four cases apt to demonstrate the variability, and the large morphological spectrum of these "myopathies" within the same family are described. In children, morphological changes are often missing. Carriers of such "subclinical myopathies" are occurring probably more frequently than supposed. Their identification in time is difficult, the only reliable methods being pharmacological fiber contraction-tests which can be performed in special laboratories only. A raw screening of patients-at-risk may be, however, achieved by exact anamnestic investigations and preoperative CPK-controls. Individuals suffering from paroxysmal myoglobinuria at any rate have to be considered patients at-risk.