Asymptomatic or minimally symptomatic hyperCKemia: histopathologic correlates.

Background: Persistent creatine kinase elevation is occasionally encountered in subjects without any clinical manifestation of a neuromuscular disorder or any condition known to be associated with increased serum CK levels. It is still unresolved whether extensive investigations and specifically a muscle biopsy should be performed in clinically normal individuals with elevated CK levels.

Objective: To study the muscle pathology of patients with asymptomatic or minimally symptomatic hyperCKemia.

Methods: The clinical and laboratory data of patients with persistent hyperCKemia and normal neurologic examination were reviewed and their muscle biopsies evaluated.

Results: The study group included 40 patients aged 7-67 years; the male to female ratio was 3:1. Nineteen patients were completely asymptomatic, 20 had mild non-specific myalgia, and 1 had muscle cramps. Electromyography was performed in 27 patients and showed myopathic changes in 7 (26%). Abnormal muscle biopsy findings (e.g., increased variation in fiber size, increased number of central nuclei, and occasional degenerating fibers) were detected in 22 of the 40 patients (55%). No fat or glycogen accumulation was detected. Immunohistochemistry demonstrated abnormal dystrophin staining in 3 patients (8%), resembling the pathologic changes of Becker muscular dystrophy. No abnormal findings were detected on immunohistochemical staining for merosin, dysferlin, caveolin 3, or alpha and gamma sarcoglycans. The EMG findings did not correlate with the pathologic findings.

Conclusions: Abnormal muscle biopsies were found in 55% of patients with asymptomatic or minimally symptomatic hyperCKemia. Specific diagnosis of muscular dystrophy, however, was possible in only 8% of the patients.