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, and while tar preparations are sometimes used, other treatments like topical steroids or biologics might be more commonly recommended.
- Eczema (nummular dermatitis): This condition could also present with erythematous lesions, although they are typically more pruritic than described in the scenario. Topical steroids are a common treatment for eczema.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Skin cancer (e.g., squamous cell carcinoma): Although the patient's spouse's concern about skin cancer might seem overly cautious, it's crucial not to miss a potentially malignant lesion. Any new or changing skin lesion, especially in an older adult, warrants careful examination and possibly a biopsy to rule out skin cancer.
- Rare diagnoses
- Tinea versicolor: This is a fungal infection that causes changes in skin pigmentation, typically presenting with hypo- or hyperpigmented macules. While it can cause some scaling, the primary complaint is usually the color change, not erythema or scaling as described. Topical selenium sulfide or antifungals might be used for treatment, but this diagnosis seems less likely given the description.