RESUMO
The genetic characteristics of the diabetic types have been assessed by following up their frequency in first degree relatives of some non-selected diabetic patients, registered at eight different centers of the country. Out of 1,003 non-diabetic controls only 46 (4.6%) had 52 diabetic relatives, 65.4% of type 2 (non-insulin-dependent). Comparatively, out of the 704 patients, 172 (24.4%) had 229 diabetic first degree relatives, 72.5 of type 2. Out of 231 type 1 (insulin-dependent) diabetic patients, 29 (12.6%) had 34 diabetic relatives, 55.9% of type 1. Out of 300 type 2 patients, 99 (33.0%) had 121 diabetic relatives, 84.0% of type 2. The other 173 diabetic patients presented an "intermediary" type of the disease (needing insulin many years after onset). Forty-four (25.4%) of them had 64 diabetic relatives, 67.2% of type 2, 20.3% of type 1 and 12.5% with "intermediary" diabetes. The five times higher frequency of diabetes in patients' relatives versus controls is pointed out. Type 2 diabetic relatives predominated. The proportion of probands with diabetic relatives increased from 4.6% in non-diabetics to 12.6% in type 1, to 25.4% in "intermediary" diabetes and to 33.0% in type 2. The heredity of type 1 prevailed in type 1 and that of type 2 in type 2 and in "intermediary" diabetes. The fact that "intermediary" diabetes tends towards type 1 (insulin-dependent) as therapy and towards type 2 (non-insulin-dependent) as heredity might be an argument supporting the controversy on the diabetic syndrome classification.
