Differential diagnosis: Skin condition in patient with 10-year history of Parkinson Disease

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A 60-year-old man who has a ten-year history of Parkinson's disease, presents with the chief complaint of “flaking skin that just does not go away, sometimes it's worse, sometimes it's better,” stating this problem has been present for more than 6 years. Concurrent health issues include hypertension, dyslipidemia, and generalized anxiety disorder. The affected areas are occasionally itchy and will ache when particularly severe. He's used over-the-counter hydrocortisone cream and skin moisturizers without seeing improvement. Physical exam reveals inflamed patches on the scalp, accompanied by greasy yellow scales. Similar lesions are noted in the nasal labial folds, behind the ears, and into the ear canals. Which of the following is the most likely diagnosis?
A. Dandruff.
B. Seborrheic dermatitis
C. Psoriasis
D. Atopic dermatitis.
And the correct answer is B. Seborrheic dermatitis.
Where should we start? First, determine what kind of question this is. Given that we're provided with the information about the patient and the clinical presentation of a skin issue of extended duration, this is a diagnosis question. As I've mentioned in other Q&A podcasts, clinical conditions with similar presentation can occur in select patient groups. In particular, all four of the derm conditions mentioned here can feature flaking skin and particularly of long duration. However, the best answer here is seborrheic dermatitis, also known as seborrhea, because this most accurately fits the overall patient scenario. Honing down to that best answer, and that's the key to passing boards, best answer involves an analysis and synthesis of factors including patient age, risk factors for a given condition, co-morbidity, as well as the clinical presentation.
Let's take a look at some background information here. Seborrheic dermatitis is a chronic recurring skin condition found in areas on the skin with a high concentration of sebaceous glands. This includes the scalp, the eyelid margins, the nasal labial folds, in and around the ears, into the ear canal is quite common, and the upper trunk. These are the areas where the characteristic skin lesions are most often found. The disease's pathophysiology is interesting in that it includes an inflammatory reaction to a yeast species that is found universally in the human scalp. However, you'll notice not everybody has seborrhea, though everyone will carry around this yeast form, only certain patients are at risk. Seborrhea is often found in patients who are immunocompromised or chronically ill, particularly older adults. And in particular, having Parkinson's Disease is a major risk factor for the development of seborrheic dermatitis. The lesions can range from a few smaller areas, with flaking, to extensive scaling lesions with thick adherent crusts. This report of the greasy yellow scaling is quite common in seborrhea. The underlying skin appears inflamed. Seborrheic dermatitis is a clinical diagnosis made by careful assessment of the patient's risk factors, history, and physical presentation. While medium potency topical corticosteroids are used for flares, these are used in conjunction with topical anti-fungal shampoos and cream for chronic treatment. This is the backbone of seborrheic dermatitis care. At the same time, you'll remember from the question that he mentions he's used over-the-counter hydrocortisone and hasn't seen any difference in the condition. Indeed, OTC hydrocortisone is so weak that it's seldom truly therapeutic. And if you've got a patient that says, Oh, when I put over-the-counter hydrocortisone on whatever it is, my chapped hands or whatever, it probably is simply the lubricating base of the hydrocortisone that's doing some good. So, let's go back and take a look at the question and the answer options.
A 60-year-old man who has a ten-year history of Parkinson's disease presents with a chief complaint of flaking skin that just doesn't go away, sometimes it's worse, sometimes it's better,” stating this problem has been present for more than six years. Concurrent health issues include hypertension, dyslipidemia, and generalized anxiety disorder. The affected areas are occasionally itchy and will ache when particularly severe. He has used OTC hydrocortisone cream and skin moisturizers without seeing improvement. Physical exam reveals inflamed patches on the scalp accompanied by greasy yellow scales. Similar lesions are noted in the nasal labial folds and behind the ears and into the ear canals. Which of the following is the most likely diagnosis?
A. Dandruff. This is not the correct answer. While dandruff does result in flaking skin lesions, usually present chronically, the lesions are limited to the scalp. In this patient, the lesions are far more extensive. Dandruff often occurs in individuals with no chronic health problems and is found nearly across the lifespan.
B. Seborrheic dermatitis. Well, of course this is the correct answer. Additional points to consider is this patient's history of Parkinson's disease, the potent seborrheic risk factor that I mentioned earlier, and his age. Most often the onset of seborrhea is between the ages of 30 to 60 years. He reports this started six plus years ago, meaning he was in his fifties with the disease onset.
C. Psoriasis. This is incorrect. While psoriasis does manifest as a chronic skin condition that can result in flaking lesions, a number of factors in its clinical presentation differ from seborrhea. Psoriasis is usually found in the extensor surfaces with the lesions most commonly found as plaques over the elbows and knees, usually covered with a silver scale, not the greasy yellow coating mentioned here. The scalp and other surfaces are sometimes involved. In more severe disease, the trunk is also involved. Psoriasis seldom affects the face, however, and that's a big part of the differential here. Psoriasis is also more common in individuals with female birth gender assignment and those with the autoimmune disease, the latter being a commonality it shares with seborrhea. Similar to seborrhea, the disease of psoriasis does tend to wax and wane. In other words, sometimes it's worse, sometimes it's better.
D. Atopic dermatitis. Another name for atopic dermatitis is eczema. While this condition can start at any age, its onset usually is in childhood or in the young adult years. A manifestation of type one hypersensitivity reaction, atopic dermatitis is most often found in individuals with other similar conditions such as allergic rhinitis or asthma. Some of the most common locations for atopic derm lesions in the older child and adult are the antecubital fossa and the popliteal space, usually presenting as slightly raised reddened areas, irregular in shape, and intensely itchy, but without any overlying scale common to many of the other chronic skin conditions we've mentioned in this question, there is a history of lesions waxing and waning.
Key takeaway: As with any differential diagnosis question, take a close look at all the information presented in the question stem or the story of the question. Risk factors for a given condition as well as the patient age and comorbidity plus the clinical presentation, will all help you steer to the best answer.
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