Differential Diagnosis for 93-year-old Female with Respiratory Symptoms and Rash
- Single most likely diagnosis:
- Viral upper respiratory infection (e.g., common cold, COVID-19): The patient's symptoms of a "really bad cold" with a cough that has mostly resolved, along with the recent advice from her PCP to get COVID testing, suggest a viral etiology. The rash could be unrelated or a nonspecific viral exanthem.
- Other Likely diagnoses:
- Allergic contact dermatitis: Despite the patient's denial of any known irritant or change in detergents, creams, or soaps, it's possible that she was exposed to something that caused an allergic reaction, leading to the pruritic rash on her left anterior chest.
- Eczema (atopic dermatitis): This condition can cause pruritic rashes and may be exacerbated by dry skin, which is common in older adults.
- Herpes zoster (shingles): Although less likely given the description of the rash as red and pruritic without mention of vesicles or a burning sensation, shingles can present atypically in older adults.
- Do Not Miss (ddxs that may not be likely, but would be deadly if missed):
- Cellulitis or soft tissue infection: While the rash is described as pruritic and not typically suggestive of a bacterial infection, it's crucial to consider cellulitis, especially in older adults, as it can rapidly progress and become severe.
- Herpes zoster with visceral involvement: If the patient has shingles, there's a risk of visceral involvement, such as herpes zoster ophthalmicus or central nervous system complications, which would require prompt antiviral treatment.
- COVID-19 with complications (e.g., pneumonia, acute respiratory distress syndrome): Although the patient's respiratory symptoms are resolving, it's essential to rule out COVID-19 and its potential complications, especially in an older adult.
- Rare diagnoses:
- Bullous pemphigoid: An autoimmune blistering disease that can present with pruritic rashes and is more common in older adults.
- Drug reaction: Although the patient doesn't mention any new medications, it's possible that a drug reaction could cause a rash, especially in older adults who may be taking multiple medications.