[Hypertrophic cardiomyopathy: never-ending complexity].

The year 1990 saw a decisive step forward in the understanding of hypertrophic cardiomyopathy (HCM)—one of the most common hereditary diseases (prevalence 1/500 families)—when it was discovered that the associated left ventricular wall hypertrophy was due to a mutation in the gene coding for the betamyosin heavy chain (MYH7),1 the main contractile protein of the sarcomere and that which forms the thick filament. Since then, more than 270 causal mutations have been described in at least 13 genes coding for sarcomere proteins; this highlights the unusual genetic complexity of this disease (http://genetics.med.harvard.edu/seidman/cg3/index.ht ml). Despite this genetic heterogeneity, HCM has a common, basic manifestation: hypertrophy of the myocardium and the risk of sudden death. The severity of the disease, however, is very variable (phenotype heterogeneity), and this can seriously hinder the establishment of a prognosis and therefore make it difficult to select patients who require aggressive treatment.2-4 Genotype determination—which as yet is a technique only available to a few laboratories that undertake research—has, however, opened up the possibility of studying the relationship between mutations and their clinical manifestations. There is hope that precise knowledge of a causal mutation will help physicians predict the severity of its associated cardiac lesions and thus help establish a prognosis. In recent years, systematic genotype-phenotype correlation studies have awakened much interest, although the information available is still scant. The work published in this issue of the REC by Laredo et al (Hospital Universitario Juan Canalejo, A Coruna) discusses this and examines whether HCM caused by mutations in the MYH7 gene are more severe than those Hypertrophic Cardiomyopathy: Never-Ending Complexity