The neurological and ophthalmological investigation of 602 members of 88 Saguenay kindreds affected by myotonic dystrophy (MyD) revealed 130 persons with a partial syndrome. These patients, whose average age was 34.1 years, showed different abnormalities such as particular ophthalmic and/or neuro-muscular signs, suggesting MyD in the absence of myotonia or typical lens abnormalities. After an average period of 2,4 years, 44 of these 130 patients were reassessed by the same neurologists and ophthalmologists. Thirty still had a partial syndrome, 8 showed a typical form of MyD and 6 no longer presented any identifiable anomaly. This preliminary follow-up study of the partial MyD syndrome did not allow us to identify any clinical anomaly from which the presence of the MyD gene could be predicted in a significant way. It furthermore suggested that the identification of equivocal or unspecific signs among these patients can sometimes lead to misdiagnosis. This must be taken into account when providing genetic counselling. It furthermore indicates that the use of DNA probes is essential for a reliable identification of asymptomatic MyD gene carriers.

The Mother and Infant with Myotonic Dystrophy Pregnancy and delivery present a number of risks for the mother suffering from myotonic dystrophy, and for her infant. Most of the time, she does not even know that she is affected by the disease and a carrier of the gene. We review the complications of pregnancy and delivery in myotonic patients, and propose a simple management with specific items for each gestational period. The child of a dystrophic mother has a 50% risk of inheriting the abnormal gene. He may also exhibit a developmental and malformation syndrome called "congenital myotonic dystrophy". From the beginning, he may show respiratory distress, thereafter inability to swallow and severely hypotonia. Later, he may demonstrate mental retardation. Some of the most obvious signs found in neonates in our practice are illustrated. We also add a few tests to the list of those already recommended for these children.

Myotonic Dystrophy: I Socio-Economic and Home-Environment Characteristics of the Patients. Myotonic dystrophy is a dominantly inherited genetic disorder which, in medical literature, has been linked to peculiar socio-economical conditions. In order to document this assertion, a sociological study was conducted in the Saguenay-Lac-Saint-Jean region (Quebec), using a representative sample (N = 218) drawn from the myotonic dystrophy population. A study of the patients' places of residence was also carried out. The results clearly indicate that myotonic dystrophy patients exhibit a socio-economic profile associated with disadvantaged milieux: high unemployment, low income and limited schooling. Many of these patients must rely on social welfare. Two families out of five (42%) live beneath the poverty line. The wage-earning history of these persons is closely linked to their self-evaluation of their working capabilities. After the age of forty, a high proportion of these people are unable to hold down a paying job and claim they are unable to do so. Within a well-screened urban area, a study of the patients' places of residence indicates census tracts where myotonic dystrophy is concentrated (ecological niches). These social areas are close to the downtown area and display characteristics of disadvantaged milieux. Accordingly, the My D gene seems to be confined to a specific socio-economic and socio-geographical environment, through which the spread of the gene is channelled among the population.

Myotonic Dystrophy: II Marriage, Fertility and Gene Transmission. A sociological study, using a representative sample (N = 218) of the myotonic dystrophy population, made possible an analysis of the relationship between certain demographic characteristics (marriage, fertility) and the mechanisms involved in the transmission of the deleterious gene. The results show a clear differentiation between the marriage rate of women and men affected by myotonic dystrophy. Whereas men show a considerable decline in marriage eligibility, women continue to marry at a young age and in a proportion almost equal to that of the unaffected population. The study also indicates that the average fertility rate among married patients in the Saguenay-Lac-Saint-Jean exceeds the fertility rate reported from affected populations found in other countries. Our study shows an above-normal male fertility rate. This demographic fact explains the overrepresentation of male transmitters noted in the affected population. However, if present trends remain unchanged, women will be more likely to transmit myotonic dystrophy to future generations. These conclusions illustrate how the transmission and spread of a dominant gene follow a pattern that cannot be dissociated from the socio-cultural characteristics taken as a whole, particularly demographic characteristics. They also provide us with useful avenues for setting up future prevention programmes.

A very high prevalence (approximately 1/475 in 1985) of myotonic dystrophy (Steinert disease) is observed in the Saguenay region, which is located in the north-east part of the Province of Quebec. For various reasons, however, the literature on the subject generally associates a high degree of selective disadvantage with this gene, which seems to contradict the Saguenay data. Using a computerized regional population register, we have reconstituted patients' genealogies and family biographies. We have thus been able to study the origin of the gene and to compare the demographic behavior of patients and controls. On the whole, patients seem to be very little disadvantaged compared to controls, in terms of reproduction as well as of geographical and occupational mobility.