An 18 year old man and his mother both presented with persistent, isolated raised serum creatine kinase (hyperCKaemia) without muscle symptoms. Analysis of caveolin-3 protein expression in muscle biopsy of the propositus showed a reduction in the protein. Genetic analysis revealed a new heterozygous mutation in the caveolin-3 (CAV-3) gene: a C-->T transition at nucleotide position 83 in exon 1 leading to a substitution of a proline for a leucine at amino acid position 28 (P28L). This is the first pathogenic mutation in the CAV-3 gene associated with isolated familial hyperCKaemia. It expands the genetic heterogeneity in patients with caveolin-3 deficiency and confirms that caveolin-3 deficiency should be considered in the differential diagnosis of isolated hyperCKaemia.