Limb-girdle muscular dystrophy type 2B misdiagnosed as polymyositis at the early stage: Case report and literature review

RATIONALE: Dysferlin myopathy is an autosomal recessive hereditary muscular dystrophy due to deficiency of dysferlin caused by alteration of the DYSF gene; Limb-girdle muscular dystrophy type 2B (LGMD2B) is the most common in Its clinical phenotypes. However, LGMD2B is rarely seen in clinical cases and may initially present as weakness of proximalpelvis muscles and muscles in the posterior compartments of thighs,which will then cause difficulty in running and limping during walking. Laboratory tests at an early stage of the disease often indicate an increased level of serum creatine kinase (CK). Moreover, polymyositis (PM) is manifested as symmetrical proximal muscle weakness of the four limbs, accompanied by an increased level of serum CK. Thus, both are very difficult to identify in clinical practice. PATIENT CONCERNS: A 25-year-old woman was admitted to our department as the limb weakness progressively worsened. She began to experience proximal muscle weakness of both lower limbs without obvious inducement, which markedly increased when she climbed the stairs or stood up after squatting. Then her symptoms worsened, with difficulty in proximal and distal lifting of the lower extremities. DIAGNOSES: Through combined immunohistochemistry and Western-blot analysis, The patient was diagnosed with LGMD2B. INTERVENTIONS: There were symptomatic treatments such as coenzyme Q10. OUTCOMES: After symptomatic treatments, the patient's symptoms were obviously relieved, and the CK level decreased. LESSONS: Through this case, we found that combined application of immunohistochemistry and Western-blot analysis is helpful in early diagnosis of LGMD2B, and a new site of frame-shift mutation in the patient's DYSF gene was found.