[One type of diabetes may conceal another].

The abrupt interruption of insulin therapy in a severely obese diabetic woman submitted to a protein-sparing modified fast in a metabolic ward led to a severe ketoacidosis. This complication occurred because the patient had type 1 rather than type 2 diabetes, and the diagnosis of ketoacidosis was delayed because of confusion between ketonuria resulting from insulin deprivation and ketonuria associated with carbohydrate and energy restriction. This case report illustrates the danger of accepting an apparently obvious diagnosis which might be in fact erroneous. More particularly, it points out the importance of a correct differential diagnosis between C-peptide positive insulin-requiring type 2 diabetes and C-peptide negative (insulin-dependent) type 1 diabetes.