## **Core Concept**
The patient's presentation of malabsorptive diarrhea, poor appetite, and specific duodenal biopsy findings such as crypt hyperplasia, villous atrophy, and the presence of CD8+ cells in the lamina propria, points towards a condition affecting the small intestine's absorptive capacity. This condition seems to involve an immune response.

## **Why the Correct Answer is Right**
The correct answer, **C. Celiac Disease**, is supported by the biopsy findings:
- **Crypt hyperplasia and villous atrophy** are hallmark features of celiac disease, a condition where the ingestion of gluten leads to damage in the small intestine.
- **CD8+ cells in the lamina propria**, along with an increased intraepithelial lymphocyte count (often CD8+), are indicative of the immune-mediated response characteristic of celiac disease.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is blank and cannot be evaluated.
- **Option B:** This option is blank and cannot be evaluated.
- **Option D:** This option is blank and cannot be evaluated.

## **Clinical Pearl / High-Yield Fact**
A key clinical pearl is that celiac disease is strongly associated with **HLA-DQ2** and **HLA-DQ8** genotypes. Patients with celiac disease typically show a good response to a **gluten-free diet**, which is the mainstay of treatment.

## **Correct Answer:** C. Celiac Disease