Israel Medical Association Journal

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[1] 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[2] 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.

Background: The prediction that Duchenne muscular dystrophy patients have out-of-frame deletions and Becker muscular dystrophy patients have in-frame deletions of the dystrophin gene holds well in the vast majority of cases. Large in-frame deletions involving the rod domain only have usually been associated with mild (BMD[1]) phenotype.

Objectives: To describe unusual cases with large in-frame deletions of the rod-shaped domain of the dystrophin gene associated with severe (Duchenne) clinical phenotype

Methods: Screening for dystrophin gene deletion was performed on genomic DNA by using multiplex polymerase chain reaction. Needle muscle biopsies from the quadriceps were obtained using a BergstrÖm needle. The biopsies were stained with histologic and histochemical techniques as well as monoclonal antibodies to dystrophin 1, 2 and 3.

Results: In three children with large in-frame deletions of the rod domain (exons 10–44, 13–40 and 3–41), early-onset weakness and a disease course suggested the DMD[2] phenotype.

Conclusions: This observation emphasizes the uncertainty in predicting the Becker phenotype in a young patient based on laboratory evaluation, and that the clinical picture should always be considered.