CAV-3-related age-dependent muscle diseases: A novel mutation in mother and son

Abstract

The caveolin-3 protein encoded by the CAV-3 gene is a muscle-specific protein found in skeletal, smooth, and cardiac muscle. Caveolin-3 defects lead to several muscle diseases: rippling muscle disease (RMD), limb-girdle muscular dystrophy (LGMD1C), distal myopathy, familial hypertrophic cardiomyopathy, and asymptomatic hyper-CK-emia. While some variants that cause mutations in this gene cause a pure type of disease, some variants may appear as overlap syndromes. Even in the same variants of CAV-3 mutation, the type of muscle disease, its severity, and time of occurrence can be variable. For this reason, it should be known that CAV-3-related diseases and all overlapping diseases can be seen over time, and the patient should be followed up. We report here a 9-year- old boy and his 38-year-old mother who were investigated for asymptomatic hyper-CK-emia and diagnosed with caveolinopathy. The boy had calf hypertrophy and percussion-induced rapid muscle contraction (PIRCs). His mother had calf hypertrophy, contractions due to percussion, and proximal muscle weakness. Mother’s proximal muscles and m. gastrocnemius magnetic resonance imaging (MRI) was normal. The mother had complaints of weakness, showing slow progression starting from the second decade. Heterozygous (ENST000003cav3849.2) c.298A>T p.Ile100Phe variant in exon 2 was detected in the CAV-3 gene. This mutation is classified as pathogenic according to The American College of Medical Genetics and Genomics (ACMG) criteria (PM1, PM2, PP3, PM5). In conclusion, calves’ pseudohypertrophy and mildly raised CK without weakness can be the initial presentation of caveolinopathy. Percussion-induced muscle contractions, rather than muscle rippling, can occur at a young age. The onset of muscle weakness can be delayed during adolescence and can have a slowly deteriorating course associated with myalgia.