Differential Diagnosis for Quarter-Sized Plaques on Arms, Legs, and Abdomen
Single Most Likely Diagnosis
- Psoriasis: This is a common skin condition characterized by well-defined, red, scaly plaques. The presence of quarter-sized plaques on the arms, legs, and abdomen is consistent with the typical distribution of psoriasis, which often affects extensor surfaces and can also involve the trunk.
Other Likely Diagnoses
- Eczema (Atopic Dermatitis): Eczema can present with plaques, although they are often more irregular and accompanied by intense itching. The distribution can vary but often involves flexural areas, though it can be widespread.
- Seborrheic Dermatitis: This condition causes scaly patches, red skin, and stubborn dandruff due to an oily scalp. It can also affect oily areas of the body, such as the face, including the eyebrows, glabella, and nasolabial folds, but can spread to other areas.
- Tinea Corporis (Ringworm): A fungal infection of the skin that can cause circular, itchy, and red plaques. It can appear anywhere on the body and is highly contagious.
Do Not Miss Diagnoses
- Cutaneous T-Cell Lymphoma (Mycosis Fungoides): A rare type of skin cancer that can mimic many other skin conditions, including eczema and psoriasis. It's crucial to consider this diagnosis, especially if the plaques are persistent and not responding to typical treatments.
- Sarcoidosis: A condition that can cause skin plaques among other systemic symptoms. Skin involvement can be the first sign of the disease, and it requires prompt diagnosis due to its potential to affect other organs.
Rare Diagnoses
- Pityriasis Rubra Pilaris: A rare skin disorder that causes constant inflammation and scaling (exfoliation) of the skin. It can start with small, rough patches on the skin and progress to cover large areas.
- Keratosis Pilaris: A condition that causes small, rough patches on the skin, often on the arms, legs, and buttocks. While not typically presenting as quarter-sized plaques, it can be considered in the differential for widespread skin lesions.
- Lichen Planus: An inflammatory condition that affects mucous membranes inside the mouth and can also affect the skin, causing purplish, itchy, flat bumps. The skin lesions can appear anywhere on the body.