Differential Diagnosis for 70-year-old with Rash

Single most likely diagnosis

• Subacute Cutaneous Lupus Erythematosus (SCLE) or Photodistributed Rash: The patient's recent history of being in a sling for 4 weeks and the location of the rash (arm, top of breasts, upper abdomen) suggest a photodistributed pattern, which is common in SCLE or other photodistributed rashes. The recent removal of the sling could have exposed these areas to sunlight, triggering the rash.

Other Likely diagnoses

• Contact Dermatitis: Given the patient's recent surgery and immobilization, she may have been exposed to new substances (e.g., soaps, lotions, or medications) that could have caused an allergic reaction, leading to contact dermatitis.
• Seborrheic Dermatitis: This condition can cause a rash in areas with high sebaceous gland activity, such as the upper chest and abdomen, and can be exacerbated by stress, immobilization, or changes in skin care.
• Tinea Versicolor: A common fungal infection that can cause a rash on the chest, back, and arms, especially in areas with high sebaceous gland activity.

Do Not Miss (ddxs that may not be likely, but would be deadly if missed)

• Malignancy (e.g., Cutaneous T-cell Lymphoma): Although less likely, it is essential to consider malignancies, such as cutaneous T-cell lymphoma, which can present with a rash and have a poor prognosis if left untreated.
• Infectious Causes (e.g., Cellulitis, Erysipelas): Bacterial infections like cellulitis or erysipelas can cause a rash and require prompt antibiotic treatment to prevent serious complications.

Rare diagnoses

• Pemphigus: A rare autoimmune disease that can cause blistering skin lesions, which may resemble a rash.
• Dermatomyositis: An inflammatory disease that can cause a rash, muscle weakness, and other systemic symptoms.
• Erythema Multiforme: A rare skin condition characterized by target-like lesions, which can be triggered by infections, medications, or other factors.