Differential Diagnosis for a Single Round Red Flaky Lesion on the Forehead
Single Most Likely Diagnosis
- Seborrheic Keratosis: A common, benign skin growth that can appear as a round, red, flaky lesion, especially on the face. Its well-defined borders and the fact that it's isolated make this a strong consideration.
Other Likely Diagnoses
- Actinic Keratosis: A precursor to skin cancer that can present as a red, flaky patch, often due to sun exposure. Although the forehead is a common location, the lack of mention of sun exposure or other risk factors makes it slightly less likely.
- Eczema/Dermatitis: Could present with redness and flakiness, but typically would be more diffuse or have a history of similar episodes.
- Psoriasis: Can cause well-defined red, scaly patches, but usually involves other areas of the body and has a more chronic course.
Do Not Miss Diagnoses
- Basal Cell Carcinoma: The most common form of skin cancer, which can present as a solitary, well-defined lesion. Early detection is crucial, making it a "do not miss" diagnosis despite its lower likelihood based on the short duration and appearance.
- Squamous Cell Carcinoma: Another form of skin cancer that can appear as a red, scaly lesion. It's less common than basal cell carcinoma but more aggressive, necessitating its consideration.
Rare Diagnoses
- Discoid Lupus Erythematosus: An autoimmune condition that can cause disk-shaped lesions, often on the face, which can be red and scaly. It's less common and usually associated with other systemic or dermatological symptoms.
- Granuloma Faciale: A rare condition characterized by single or multiple, well-defined, red to purple plaques on the face, which could potentially present similarly but is much less common.
- Cutaneous T-Cell Lymphoma (Mycosis Fungoides): A rare form of skin cancer that can present with a variety of skin lesions, including patches, plaques, or tumors. It's an unlikely diagnosis for a single, well-defined lesion but should be considered in the differential due to its potential severity.