P.148 - A case of caveolinopathy presenting as the mounding muscle disease

Abstract

Caveolin 3 is a membrane protein at caveolae of skeletal muscles. It participates in the membrane stabilization and the signaling pathways. Five clinical features of caveolinopathy have been reported: limb girdle muscular dystrophy 1C, isolated hyperCKemia, rippling muscle disease, distal myopathy and familial hypertrophic cardiomyopathy. This is a second report of genetically confirmed caveolinopathy case in South Korea. A 20-year-old man visited our clinic complaining exercise-induced muscle stiffness. When he was 10 years old, he began to feel stiffness in his proximal legs on running. He often noticed mounding on his thigh muscles. Stiffness and mounding tended to resolve within 10 seconds. The patient also stated wake-up stiffness and infrequent muscle rippling. His elder brother and mother as well as maternal grandmother and uncle shared his symptoms. Neurologic examination revealed tap-induced muscle mounding and bilateral calf hypertrophy, while other features of myopathy lacked. Serum creatine kinase was elevated, and needle EMG showed chronic myopathic pattern. Interestingly, tap-induced spontaneous activity was recorded on EMG. There were no myotonic discharges or decremental responses in short exercise test. Muscle biopsy revealed nonspecific myopathic pattern with moderate fiber size variation, regenerating fibers and internal nuclei. Focused exome sequencing detected a heterozygous CAV3 mutation (p.R27Q) with a known pathogenicity. We find mere mounding of skeletal muscle on exercise or tap could also be a feature suggestive of caveolinopathy.