Differential Diagnosis for Rash on Left Lower Leg
- Single most likely diagnosis
- Contact Dermatitis: Given the history of rashes with stress and the appearance of the rash over scar tissue, contact dermatitis is a strong consideration. The severe itching, soreness, and swelling also align with this diagnosis. The lack of response to hydrocortisone cream does not rule out contact dermatitis, as it can be resistant to topical steroids, especially if the offending agent is still present.
- Other Likely diagnoses
- Eczema (Atopic Dermatitis): The patient's history of rashes with stress and the current symptoms of itching, soreness, and swelling could suggest eczema, particularly if the stress is exacerbating an underlying atopic tendency.
- Cellulitis: Although the patient mentions the rash is over scar tissue, the presence of severe itching, soreness, swelling, and the lack of response to hydrocortisone cream could also indicate a bacterial infection like cellulitis, especially if the scar tissue has become infected.
- Allergic Reaction: An allergic reaction to a substance (e.g., a new soap, lotion, or insect bite) could cause a rash, itching, soreness, and swelling, and the fact that it's localized to one area (the left lower leg) supports this possibility.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Deep Vein Thrombosis (DVT): While the primary complaint is a rash, the swelling and soreness could also be indicative of a DVT, which is a medical emergency. The history of an injury could potentially increase the risk for DVT.
- Necrotizing Fasciitis: Although rare, this condition is a medical emergency that can present with severe pain, swelling, and sometimes a rash, and can quickly progress to life-threatening if not treated promptly.
- Rare diagnoses
- Erythema Multiforme: A skin condition characterized by target lesions, which could present with a rash, but it's less likely given the description and the localized nature of the symptoms.
- Pyoderma Gangrenosum: A rare skin condition that can cause painful ulcers, but it's less common and typically has a more distinctive appearance than what's described.