What is the characteristic of the immune-mediated type 1 diabetes mellitus?

A. Oral agents are often effective for treatment is incorrect because type 1 diabetes is characterized by autoimmune destruction of pancreatic beta cells, leading to absolute insulin deficiency. Insulin therapy, not oral hypoglycemic agents, is required. B. Age at onset is usually younger than 18 years is correct because immune-mediated type 1 diabetes typically develops in children and adolescents, although it can occur at any age. This is the classic age group for presentation of type 1 diabetes. C. Onset is gradual is incorrect because type 1 diabetes usually has a rapid onset of symptoms, such as polyuria, polydipsia, weight loss, and fatigue, over weeks to months. D. Ketoacidosis is infrequent is incorrect because diabetic ketoacidosis (DKA) is a common presenting feature in children with type 1 diabetes, especially at initial diagnosis, due to absolute insulin deficiency.