Differential Diagnosis for the 87-year-old Female Patient
- Single most likely diagnosis
- Herpes Zoster (Shingles): The patient's description of a painful, itchy rash on one side of her head, above her ear, which began about 2 days ago, is highly suggestive of shingles. The rash's characteristics, including its location and the patient's age, further support this diagnosis. Shingles typically presents as a unilateral rash that does not cross the midline, often accompanied by pain and itching.
- Other Likely diagnoses
- Contact Dermatitis: Given the patient's report of irritation for the past week and the initial attempt to treat the rash with Neosporin, contact dermatitis is a possible diagnosis. This condition could result from an allergic reaction or irritant exposure, leading to a rash that can be itchy and painful.
- Eczema (Atopic Dermatitis): Eczema can cause itchy, burning rashes and can occur at any age, including in the elderly. Although less likely given the acute onset, it remains a consideration, especially if the patient has a history of atopic diseases.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed.)
- Cellulitis: While the patient's symptoms do not strongly suggest cellulitis, it is crucial not to miss this diagnosis due to its potential for serious complications, including sepsis. Cellulitis can present with redness, swelling, and warmth of the skin, often accompanied by fever and malaise.
- Erythema Migrans (Lyme Disease): Although less common in this presentation, erythema migrans, the rash associated with Lyme disease, can sometimes be mistaken for other conditions. It is essential to consider Lyme disease, especially if the patient has been exposed to ticks, due to its potential for serious long-term consequences if left untreated.
- Rare diagnoses
- Bullous Pemphigoid: This is an autoimmune skin disease that can cause blistering rashes, which might be painful and itchy. It is more common in the elderly but is less likely given the description of the rash.
- Dermatomyositis: An inflammatory disease characterized by skin rash and muscle weakness. The rash can be itchy and painful, but the presence of muscle weakness and other systemic symptoms would typically accompany it, making it less likely in this scenario.