A 15-year-old boy presents to the nurse practitioner with polyuria, polydipsia, and weight loss. The NP diagnoses diabetic ketoacidosis resulting from undiagnosed type 1 diabetes mellitus (T1DM). What is the pathophysiology underlying T1DM?

Choice A reason: Insulin resistance is the hallmark of type 2 diabetes mellitus, not type 1. In type 1 diabetes, the issue is not resistance to insulin but rather a lack of insulin production due to destruction of beta cells. Choice B reason: Type 1 diabetes is not caused by a single genetic mutation nor is it inherited in an autosomal dominant fashion. While genetic predisposition plays a role, it involves multiple genes and environmental triggers leading to autoimmune destruction. Choice C reason: Secondary diabetes can result from pancreatic diseases, hormonal disorders, or medications, but this is classified as type 3c diabetes or drug-induced diabetes. It is not the mechanism underlying classic type 1 diabetes. Choice D reason: Type 1 diabetes is an autoimmune condition where the immune system mistakenly attacks and destroys insulin-producing beta cells in the pancreas. This leads to absolute insulin deficiency, hyperglycemia, and in severe cases, diabetic ketoacidosis.