Comments on Hesslow’s ‘What is a Genetic Disease?’

Abstract

I agree with Hesslow in what I take to be his main conclusion: diseases are determined by both genetic and environmental factors, and the importance which we attach to different factors depends on our choice of causal field. This is an important message, as the clinician who stares himself blind at the genetic factor may well overlook that it is possible to prevent or cure the disease by the elimination of a necessary environmental factor. However, Hesslow may be going a bit too far. The paper is entitled ‘What is a genetic disease?’, and the reader is left with the impression that it is simply a matter of choice whether or not a disease is labelled as genetic. In this comment I shall suggest what I consider to be reasonable definitions of the concept of genetic disease, and I shall discuss a number of examples. First, we should consider the situation where a genetic abnormality is a necessary and a sufficient determinant of a disease regardless of the environment. As an example I can mention Klinefelter’s syndrome. Individuals with this syndrome are males with one or more extra X chromosomes, and it seems quite unlikely that any alteration of the environment can prevent the development of this disease. Of course diseases are never monocausal, and the abnormality itself may be determined by a multitude of factors, some environmental and other genetic, but that is a different story. Diseases like Klinefelter’s syndrome are genetic diseases in the strongest sense.