Calf hypertrophy and gastrocnemius MRI short tau inversion recovery (STIR) hyperintensity in a patient with asymptomatic hyperCKemia caused by caveolin-3 gene mutation

Abstract

We present a 16-year-old man with asymptomatic hyperCKemia fluctuating between 900 and 2400 IU/L. His parents and his younger sister (13-year-old) were asymptomatic. Clinical examination showed no abnormalities apart of bilateral calf hypertrophy (calf circumference of 41 cm in both legs) (Fig. 1) [1]. Electromyography showed no abnormalities at rest, and small amplitude, brief, polyphasic action potentials, and early recruitment after muscle contraction in the proximal limb muscles. Lower limb muscle MRI (performed in the absence of unusual physical activity, exercise, or trauma preceding the MRI) confirmed calf hypertrophy and showed STIR hyperintensities in the bilateral medial gastrocnemius muscles (predominant on the right side) in the absence of abnormalities on T1-weighted imaging (Fig. 1), while the thighs did not show any abnormalities. Muscle biopsy of the right-sided medial gastrocnemius muscle showed myopathic changes (pathological fibre size variation, atrophic fibres, necrosis-regeneration, increased endomysial connective tissue, nuclear centralisation, core-like lesions) and immunohistochemical analyses showed normal expression of dystrophin, sarcoglycanes, dystroglycanes, merosin and nearly complete absence of caveolin-3 expression