Differential Diagnosis
- Single most likely diagnosis
- Actinic keratosis: This is the most likely diagnosis given the description of erythematous scaly macular lesions on the left forearm of an older adult. Actinic keratosis is a common skin condition caused by prolonged exposure to sunlight, leading to the formation of small, rough, sandpapery patches on the skin. The fact that the lesions are not pruritic and have been present for some time also supports this diagnosis. Cryotherapy is a recommended treatment option for actinic keratosis.
- Other Likely diagnoses
- Psoriasis: Although the patient's lesions are not described as being on typical areas for psoriasis (elbows, knees, scalp), it is still a possible diagnosis. Psoriasis can present with erythematous scaly lesions, but it is often accompanied by pruritus, which is not present in this case.
- Eczema (nummular dermatitis): This condition can cause erythematous scaly lesions, but it is often pruritic, which does not match the patient's symptoms.
- Tinea versicolor: Although this condition can cause macular lesions, it typically presents with hypo- or hyperpigmented patches, and the patient's symptoms do not fully align with this diagnosis.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Skin cancer (squamous cell carcinoma or basal cell carcinoma): Although the patient's spouse is concerned about skin cancer, the description of the lesions does not strongly suggest this diagnosis. However, it is essential to consider skin cancer in the differential diagnosis, as it can be life-threatening if left untreated.
- Rare diagnoses
- Cutaneous T-cell lymphoma (mycosis fungoides): This is a rare condition that can cause erythematous scaly lesions, but it is often accompanied by other symptoms such as pruritus, and the patient's presentation does not strongly suggest this diagnosis.
- Other rare skin conditions (e.g., parapsoriasis, pityriasis rubra pilaris): These conditions can cause erythematous scaly lesions, but they are relatively rare and would require further evaluation to diagnose.