A 67-year-old man with Parkinson disease has macular areas of erythema with a greasy scale behind the ears and on the scalp, eyebrows, glabella, nasolabial folds, and central chest. Which of the following is true?

Okay, let's tackle this question. The patient has Parkinson's disease and presents with specific skin lesions. The key areas mentioned are the ears, scalp, eyebrows, glabella, nasolabial folds, and central chest. These are all seborrheic areas, which makes me think of seborrheic dermatitis.

Seborrheic dermatitis is common in people with Parkinson's because of the association with increased sebum production and Malassezia yeast. The symptoms described—erythema with greasy scales—fit this condition. The clinical pearl here is that Parkinson's patients are more prone to seborrheic dermatitis due to their disease and medications, like anticholinergics which can affect skin health.

Looking at the options, the correct answer would link the condition to seborrheic dermatitis. The other options might suggest other dermatoses like psoriasis or eczema, but those don't typically present with the greasy scale and specific distribution. Also, fungal infections could be a consideration, but the chronic nature and location point more to seborrheic dermatitis.

So, the core concept is recognizing the clinical presentation and understanding the association with Parkinson's disease. The correct answer is likely about seborrheic dermatitis being the diagnosis. The other options would be incorrect because they don't match the presentation or the patient's underlying condition.

**Core Concept**
This question assesses the recognition of **seborrheic dermatitis**, a chronic inflammatory skin condition associated with **Malassezia yeast overgrowth** and **sebum-rich areas**. Parkinson’s disease patients are particularly susceptible due to **anticholinergic medications** and **neurological dysfunction** affecting skin barrier integrity.

**Why the Correct Answer is Right**
Seborrheic dermatitis presents with **erythematous, greasy scales** in sebum-rich zones (scalp, nasolabial folds, eyebrows, chest). In Parkinson’s disease, **anticholinergic therapies** (e.g., benztropine) reduce sweating and sebum regulation, promoting Malassezia proliferation. The **T cells** in the skin react to yeast antigens, causing inflammation. Clinical features include **lichenification** and **relapsing courses**, worsening with stress or immunosuppression.

**Why Each Wrong Option is Incorrect**
**Option A:** *Psoriasis* lacks greasy scales and typically shows **silvery plaques** with **Koebner phenomenon**; it’s less linked to Parkinson’s.
**Option B:** *Contact dermatitis* would have a **clear history of allergen exposure** and **erythematous vesicles**, not greasy scales.
**Option C:** *Fungal infections* (e.g., tinea) require **dermatophytes**, not Malassezia; they show **edge-dominant scaling** and **positive KOH test**.

**Clinical Pearl / High-Yield Fact**
**Parkinson’s patients on anticholinergics** are at high risk for **seborrheic dermatitis**. Treat with **antifungal shampoos (ketoconazole)** and **low-potency corticosteroids**. Avoid systemic antifungals due to drug interactions with Parkinson’s medications.

**Correct Answer: C. Sebor

✓ Correct Answer: D. Topical ketoconazole or 1% hydrocortisone cream (low potency) is good initial therapy.