Hueston (1985c, 1990a) has observed that certain features of Dupuytren's disease dictate a more aggressive course of the disease as well as a greater tendency for recurrence after operation. He thinks that the patients showing those features have a greater expression of the disease or diathesis. Quoting the Oxford English Dictionary, he defines the diathesis as "a permanent condition of the body which renders it liable to a special disease". He ascribes, rather empirically, the appearance of new Dupuytren's tissue either in an operatively cleared zone (recurrence) or beyond the area of operation (extension) to the strength of the diathesis. It is therefore manifestly important to assess as well as possible the factors indicating that strength.
Beside a racial factor, he recognises four signs of a strong diathesis: an early onset of the disease, bilaterality, a positive family history and the involvement of other areas.
The incidence in northern Europe is higher than in the Mediterranean basin. In Italy there is a far higher incidence in the north than below Naples. This is consistent with the introduction of a genetic predisposition in the north-west from French and in the north-east from Austro-Hungarian invasions (Hueston, 1990a). Hueston (who worked in Melbourne) reports that despite the fact that Australia has the greatest Greek population outside Greece, he has seen only one Greek male with very mild Dupuytren's disease who on questioning revealed that his mother was Irish!
An explanation of this north-west European dominance of Dupuytren's disease has been that it was in the genetic spectrum of the Celts. More likely, in view of their wide raiding patterns, it could be regarded as a Viking disease (Hueston, 1985c; Whaley et al.,1993).
The Nordic origin of the disease was first suggested by Early (1962) who made a comparison of its incidence in various countries and found that it was highest in Denmark. He also suggested that "if one postulates the condition as having arisen in one particular racial group then the variable distribution in other parts of the world might be explained on the basis of migration from that group". The identification (Whaley et al., 1993) of four miracle cures in the Icelandic sagas, which constitute a large part of the written tradition of mediaeval Scandinavia, in which the condition of the hand which was healed bears a resemblance to Dupuytren's disease suggest that the Norsemen may have suffered from the contracture. A study by Brouet (1986) in Toulon has noted a striking difference in the incidence of Dupuytren's disease in the dark-eyed Mediterraneans and that in the blue-eyed population of Nordic origin. A far stronger diathesis was observed in the Toulonese of Nordic than of local Mediterranean origin. Beside the observations of Brouet, the Nordic theory of origin is further supported by the apparently high incidence of the condition in those parts of Great Britain which faced the Norsemen, namely north-east England and the north and west of Scotland both of which were invaded and subsequently colonised, the former permanently and the latter for nearly 500 years (Elliot, 1988a).
The high incidence of the disease in Canada and the United States can easily be explained by the migration from the British Isles. The same Scottish and Irish predominance in the early white settlers in Australia and New Zealand explains the incidence in these countries as well.
In Japan, the demography of the condition has not yet been precisely established but from Egawa's results it seems that the disease is as prevalent in Japanese people as in Australian, British or Norwegian populations (Egawa, 1990). Egawa noted, however, that either the progression of the disease is slower in Japanese than in European people, or that the disease has a later onset in the Japanese population. Few Japanese patients progress to surgery for correction of the deformity.
The presence of the disease in races other than those of obvious North European descent probably represents isolated genetic events and has no bearing on the argument as to whether most cases today arise within the gene pool disseminated by the Norsemen. Indeed, the disease in Europe must have arisen earlier in history by the process of mutation.
For Hueston, a bilateral disease would also suggest a stronger diathesis but McFarlane found that this factor, acting alone, had no effect on the course of the disease.
As pointed out by McGrouther (1990c), this is hardly surprising in a non-lethal condition which often has an onset in later life and when many, perhaps most, of those affected do not seek treatment. Moreover the patients are often unaware of early signs of the disease and it would be surprising if relatives were more sensitive.
The most detailed analysis of the familial nature of Dupuytren's disease is that of Ling (1963) who examined 832 relatives of 50 patients in Edinburgh. He noted that the number of affected relatives rose from 16 % on history taking to 68 % after examination of relatives thus demonstrating the little statistical value that can be placed on the familial incidence as suggested by history alone. Ling's conclusion, corroborated by James (1985) who reports a study made by Thieme, was that a single gene, behaving as autosomal dominant, was likely to be involved.
Ling and Thieme, however, made their studies in Edinburgh were the incidence of Dupuytren's disease is high. None of the cases reported by Egawa (1990) in Japan, Mennen (1986) in South African negroes, Srivastava (1989) in Asiatic Indians or Yih Liu (1991) in Chinese of Taiwan had relatives affected by the disease.
The idea of a Dupuytren diathesis, the term expressing a predisposition, is hard to define and has done little to clarify the situation. An index of the severity of the disease partially based on such proven unreliable factors as the existence of a positive family history or an early onset of the disease, cannot be very useful to establish the most appropriate treatment. We clearly need more objective data because as stated by McGrouther (1988) "all of these rather empirical views highlight the muddled thinking which prevails on pathogenesis and treatment".