Cardiomyopathy in Africa: heredity versus environment

Abstract

Unlike other parts of the world in which cardiomyopathy is rare, heart muscle disease is endemic in Africa. The major forms of cardiomyopathy in Africa are dilated cardiomyopathy (DCM) and endomyocardial fibrosis (EMF). Whereas DCM is a major cause of heart failure throughout the continent, EMF is restricted to the tropical regions of East, Central, and West Africa. Although epidemiological studies are lacking, hypertrophic cardiomyopathy and arrhythmogenic right ventricular cardiomyopathy seem to have characteristics similar to those of other populations elsewhere in the world. Recent advances in the genetic analysis of DCM in other parts of the world indicate that it is a genetically heterogeneous disorder in which some cases have a Mendelian cause and others have a non-genetic or multifactorial cause. This heterogeneous pattern of inheritance has been confirmed in small studies that have been conducted so far in Africa. The advent of human immunodeficiency virus infection and its association with cardiomyopathy has emphasised the role of inflammatory agents in the pathogenesis of DCM. By contrast with DCM in which some cases have major genetic contributions, there is scanty evidence for the role of genetic factors in the aetiology of EMF. Although the pathogenesis of EMF is not fully understood, it appears that the conditioning factor may be geography (in its widest sense, to include climate and socio-economic status), the triggering factor may be an as yet unidentified infective agent, and the perpetuating factor may be eosinophilia. There is a need for renewed effort to identify genetic and non-genetic factors in EMF and other forms of heart muscle disease that are prevalent on the continent of Africa.

Fig. 1.

The geographic distribution of endomyocardial fibrosis in Africa is shown in the shaded area. Arrows indicate the location of major centres of research in this disease.

Fig. 2.

Survival of 46 necropsy cases of EMF patients after first symptoms.

Fig. 3.

Genetic and environmental contribution to cardiomyopathy occurs along a continuum. HCM, hypertrophic cardiomyopathy; ARVC, arrhythmogenic right ventricular cardiomyopathy; DCM, dilated cardiomyopathy; EMF, endomyocardial fibrosis. (Courtesy of Prof H Watkins, University of Oxford.)