Analysis of Dysferlin Protein Levels May Help Diagnose Miyoshi Myopathy

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by Joana Fernandes |

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Detection of the protein dysferlin may help doctors diagnose cases of Miyoshi myopathy (MM), a muscular disorder that primarily affects muscles of the hands and feet, according to a case study published in the journal Experimental And Therapeutic Medicine.

In the study, “Atypical Miyoshi Distal Myopathy: A Case Report,” the authors report the case of a patient with atypical symptoms of MM who was originally misdiagnosed, but whose correct diagnosis was made possible due to biochemical analysis of dysferlin levels.

MM is caused by mutations in the gene encoding the protein dysferlin, a muscle protein, thus blocking its production in muscle cells. This condition initially affects the gastrocnemius or soleus muscle, making it difficult to stand on the tiptoes. Clinical manifestations usually occur in the period between the late teens and the age of 30.

The study describes the case of a 37-year-old man who went to the doctor complaining of difficulties in walking upstairs or standing when that required putting pressure on his left foot. He also had no neurological symptoms or anomalies in muscle tone, strength, and sensation. However, laboratory analyses indicated increased levels of blood creatine kinase (CK), usually elevated in muscle diseases.

Doctors diagnosed the patient with inflammatory myopathy and prescribed him dexamethasone (10 mg) for five days, with gradual discontinuation of the treatment. As no improvement was seen, doctors decided to biopsy the patient’s left quadriceps muscle and perform several biochemical analyses, including analysis of cell death, inflammation, dystrophin and dysferlin levels. Results indicated there was no sign of dysferlin in his cells, which contributed to the diagnosis of MM.

“The patient of the present study reported no family history of Miyoshi myopathy,” the authors wrote. “One clinical manifestation in the present case was the inability to stand on tiptoe on the left foot. Progressively, the CK levels in the patient’s peripheral blood increased markedly. … These clinical manifestations are suggestive of a diagnosis of distal MM,” they wrote.

According to the authors, biochemical analysis for the detection of dysferlin may help doctors make an accurate diagnosis of MM and distinguish between this disease and others that share common inflammatory symptoms in patients with muscular weakness.