Israel Medical Association Journal

Background: Myotonic dystrophy type 2 (DM2) is an autosomal dominant, multisystem disorder caused by a CCTG tetranucleotide repeat expansion located in intron 1 of the zinc finger protein 9 gene (ZNF9 gene) on chromosome 3q 21.3.

Objectives: To describe the clinical, electrophysiologic and pathologic findings in patients with myotonic dystrophy 2.

Methods: We evaluated 10 patients genetically, clinically and electrophysiologically during the years 2007 to 2008.

Results: All patients were of Jewish European ancestry. Among affected individuals, eight patients had symptoms of proximal muscle weakness, two had muscle pain, and two exhibited myotonia. On physical examination six patients had severe weakness of hip flexor muscles. Seven individuals underwent cataract surgery, and cardiac involvement was seen in one case. On the initial electromyographic (EMG) examination five patients demonstrated myotonic discharges; repeated studies showed these discharges in nine cases. Six muscle biopsies showed non-specific pathological changes. Seven patients had an affected first-degree relative with either a diagnosed or an undiagnosed muscular disorder, consistent with an autosomal dominant trait.

Conclusions: DM2 may often present with proximal muscle weakness without myotonia. EMG may initially fail to show myotonic discharges, but these discharges may eventually show in most cases on repeated EMG. Thus, DM2 may be underdiagnosed and should be included in the differential diagnosis of adult patients of Jewish European ancestry presenting with proximal lower limb weakness.
 

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.