**Question:** A 14-year-old boy presents for a pre-summer camp physical examination. Routine urinalysis discloses 3+ glucosuria. He admits to thirst and frequent urination, accompanied by a 4-kg (9-lb) weight loss over past few months. His parents note that he had a flu-like illness 5 months ago. His blood glucose is 220 mg/dL. Which of the following best explains the pathogenesis of hyperglycemia in this patient?

A. Autoimmune destruction of pancreatic beta cells (Type 1 diabetes mellitus)
B. Infection-induced insulin resistance (post-infectious diabetes)
C. Insulin resistance (Type 2 diabetes mellitus)
D. Genetic predisposition (asymptomatic polygenic diabetes)

**Correct Answer:** B. Infection-induced insulin resistance (post-infectious diabetes)

**Core Concept:**

The patient's symptoms and laboratory findings indicate the presence of hyperglycemia, which can be explained by the pathogenesis of post-infectious diabetes. Post-infectious diabetes is a condition characterized by hyperglycemia following an acute infection, such as the one he experienced 5 months ago. This type of diabetes is believed to be caused by the release of pro-inflammatory cytokines during the acute infection, which leads to insulin resistance.

**Why the Correct Answer is Right:**

The patient's symptoms, such as glucosuria, thirst, frequent urination, and weight loss, are indicative of hyperglycemia. The significant blood glucose level of 220 mg/dL further supports this diagnosis.

Post-infectious diabetes, also known as post-viral diabetes, is triggered by an acute infection that leads to the release of pro-inflammatory cytokines. These cytokines cause insulin resistance, which results in hyperglycemia. In this case, the patient's acute infection 5 months ago could have triggered the release of cytokines, causing insulin resistance and ultimately leading to hyperglycemia.

**Why Other Options are Incorrect:**

A) Type 1 diabetes mellitus (autoimmune destruction of pancreatic beta cells) is unrelated to the presented symptoms and findings, as the patient is young and has no history of family diabetic history, which rules out a polygenic predisposition.

C) Type 2 diabetes mellitus (insulin resistance due to obesity and/or genetic predisposition) is unlikely in this patient, as he is young, has no history of obesity, and no family history of diabetes.

D) Polygenic diabetes is an umbrella term for various types of diabetes, which do not fit the patient's presentation. The patient's symptoms, glucosuria, and elevated blood glucose levels indicate post-infectious diabetes (post-viral diabetes), which is triggered by an acute infection and results in insulin resistance leading to hyperglycemia. In this case, the acute infection 5 months ago could have triggered the release of cytokines, causing insulin resistance and ultimately leading to hyperglycemia.