n Cardiovascular Journal of Africa - Diagnostic disparity and identification of two gene mutations, one novel and one arising , in South African patients with restrictive cardiomyopathy and focal ventricular hypertrophy : cardiovascular topic

Volume 26, Issue 2
  • ISSN : 1995-1892
  • E-ISSN: 1680-0745



The minimum criterion for the diagnosis of hypertrophic cardiomyopathy (HCM) is thickening of the left ventricular wall, typically in an asymmetrical or focal fashion, and it requires no functional deficit. Using this criterion, we identified a family with four affected individuals and a single unrelated individual essentially with restrictive cardiomyopathy (RCM). Mutations in genes coding for the thin filaments of cardiac muscle have been described in RCM and HCM with 'restrictive features'. One such gene encodes for cardiac troponin I (), a sub-unit of the troponin complex involved in the regulation of striated muscle contraction. We hypothesised that mutations in could underlie this particular phenotype, and we therefore screened for mutations in 115 HCM probands.

Clinical investigation involved examination, echocardiography, chest X-ray and an electrocardiogram of both the index cases and close relatives. The study cohort consisted of 113 South African HCM probands, with and without known founder HCM mutations, and 100 ethnically matched control individuals. Mutation screening of for disease-causing mutations were performed using high-resolution melt (HRM) analysis.
HRM analyses identified three previously described HCM-causing mutations (p.Pro82Ser, p.Arg162Gln, p.Arg170Gln) and a novel exonic variant (p.Leu144His). A previous study involving the same amino acid identified a p.Leu144Gln mutation in a patient presenting with RCM, with clinical features of HCM. We observed the novel p.Leu144His mutation in three siblings with clinical RCM and varying degrees of ventricular hypertrophy. The isolated index case with the p.Arg170Gln mutation presented with a similar phenotype. Both mutations were absent in a healthy control group.
We have identified a novel disease-causing p.Leu144His mutation and a p.Arg170Gln mutation associated with RCM and focal ventricular hypertrophy, often below the typical diagnostic threshold for HCM. Our study provides information regarding mutations underlying RCM in contrast to other causes of a similar presentation, such as constrictive pericarditis or infiltration of cardiac muscle, all with marked right-sided cardiac manifestations. This study therefore highlights the need for extensive mutation screening of genes encoding for sarcomeric proteins, such as to identify the underlying cause of this particular phenotype.

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