**Question:** All of the following are diagnostic criteria of allergic fungal sinusitis (AFS) except:

A. Mucosal thickening and polyposis in the involved sinuses
B. Fungal elements within the mucosa
C. Type 1 hypersensitivity reactions
D. Radiological evidence of sinusitis

**Core Concept:** Allergic fungal sinusitis (AFS) is a subtype of chronic sinusitis characterized by a combination of allergic reactions and fungal colonization. The diagnostic criteria involve various aspects such as clinical presentation, radiological findings, and histopathological evidence.

**Why the Correct Answer is Right:** Option D, "Radiological evidence of sinusitis," is not considered a specific diagnostic criterion for AFS. AFS typically presents with mucosal thickening and polyposis (Option A), fungal elements within the mucosa (Option B), and type 1 hypersensitivity reactions (Option C). Radiology findings can support the diagnosis but are not the primary criteria.

**Why Each Wrong Option is Incorrect:**

A. Mucosal thickening and polyposis in the involved sinuses (Option A): These are indicative of AFS, as they represent the histopathological changes and clinical presentation in the affected sinuses.

B. Fungal elements within the mucosa (Option B): This is another essential feature of AFS, as the presence of fungal elements confirms the fungal involvement and supports the diagnosis.

C. Type 1 hypersensitivity reactions (Option C): Type 1 hypersensitivity reactions are crucial in understanding the pathophysiology of AFS, as they demonstrate the allergic component of the condition.

**Clinical Pearl:** AFS is a complex disorder with a combination of allergic and fungal components. The diagnostic criteria involve clinical presentation, histopathological findings, and radiological support. While radiology can help confirm the diagnosis, it is not a standalone criterion. A combination of mucosal changes, fungal elements, and allergic reactions is essential for the diagnosis of allergic fungal sinusitis.

**Correct Answer:** D. Radiological evidence of sinusitis

**Explanation:** The correct answer is D because radiological findings, although supportive, are not specific diagnostic criteria for AFS. AFS is characterized by mucosal thickening, polypoid lesions, and fungal elements within the mucosa, which are not mentioned in option D. These features are crucial for the diagnosis, while radiology may provide additional information but is not the primary basis for diagnosis.