Onset is variable. Classically, in younger age groups, the classical onset is acute and insulin is needed for survival – generally present with a history of thirst, polyuria, polydipsia, lethargy and weight loss over a period of up to two weeks – many may present with ketoacidosis. Also may have muscular cramps, blurring of the vision and infections. Clinical signs are usually on present for a few weeks.
5-10% will present with ketoacidosis – dehydration; marked polydipsia and polyuria; loss of skin turgor; tachycardia; hypotension; deep and sighing breath (usually smells of acetone); reduced level of unconsciousness. Needs immediate hospitalisation. Intercurrent illness may cause the apid metabolic decompensation leading to the ketoacidosis; C-peptide will be absent.
In older age groups onset is more insidious (may be misclassified as type 2 initially) – residual beta cell function lessens risk of ketoacidosis at time of presentation; lower levels of autoantibodies are found in adult onset types; weight loss is less; less likely to develop ketoacidosis;
Tissue damage complications are not present at time of diagnosis.
Need exogenous insulin for survival.
Honeymoon phase – despite severe decrease in insulin secretion at time of diagnosis, there is a period of 6-12 months of increased insulin secretion following start of exogenous insulin therapy.