Differential Diagnosis for 76-year-old Asian Male with Dark Rash on Lower Back
Single Most Likely Diagnosis
- Tinea corporis (ringworm): A common fungal infection that can cause a dark, circular rash on the skin, including the lower back. The patient's age and the location of the rash make this a plausible diagnosis.
Other Likely Diagnoses
- Contact dermatitis: An allergic or irritant reaction to something that has come into contact with the skin, potentially causing a dark rash on the lower back.
- Seborrheic dermatitis: A chronic skin condition that can cause a dark, scaly rash, particularly in areas with high sebaceous gland activity, such as the lower back.
- Eczema (atopic dermatitis): A chronic skin condition characterized by itchy, inflamed skin, which can sometimes appear as a dark rash on the lower back.
Do Not Miss Diagnoses
- Malignant melanoma: Although less likely, a new, dark skin lesion on the lower back could be a sign of skin cancer, which would be critical to diagnose early.
- Sepsis or meningitis (in the context of a rash like meningococcemia): Certain infections can cause a rash, and while rare, these conditions are life-threatening and should not be missed.
Rare Diagnoses
- Erythema multiforme: A rare skin condition characterized by target-like lesions, which could potentially appear as a dark rash on the lower back.
- Fixed drug eruption: A rare condition where a medication causes a skin reaction, resulting in a dark, circular lesion that recurs at the same site each time the medication is taken.
- Dermatological manifestations of systemic diseases (e.g., amyloidosis, porphyria cutanea tarda): Certain systemic diseases can have skin manifestations, including dark rashes, though these would be less common and might require further investigation to diagnose.