Although Parkinson disease (PD) is often characterized as a motor disorder, the presence of nonmotor symptoms, such as skin disorders, is common and may provide insights into the pathophysiological mechanisms underlying PD.
Although Parkinson disease (PD) is often characterized as a motor disorder, the presence of nonmotor symptoms, such as skin disorders, are common and may provide insights into the pathophysiological mechanisms underlying PD, said Nicki Niemann, MD, neurologist at the Muhammad Ali Parkinson Center and an assistant professor of neurology at Barrow Neurological Institute.
AJMC®: Hello, I'm Matthew Gavidia. Today on the MJH Life Sciences’ Medical World News, The American Journal of Managed Care® is pleased to welcome Dr Nicki Niemann, neurologist at the Muhammad Ali Parkinson Center and an assistant professor of neurology at Barrow Neurological Institute. Dr Niemann additionally served as a co-author of a review article titled “Parkinson's Disease and Skin.”
Great to have you on, Nicki. Can you just introduce yourself and tell us a little bit about your work?
Dr Niemann: So, I'm a neurologist by training. I did my training at Baylor College of Medicine in Houston, Texas, and then I did my mood disorders fellowship with the same institution under the mentorship of Dr Joseph Jankovic, who's one of the co-authors on the review article that we're talking about today.
I'm originally from Denmark, where I was born and raised and where I went to medical school at the University of Copenhagen before relocating to first Texas and now here in Phoenix, Arizona, for work.
AJMC®: To get us started, can you first speak on the association and nature of skin disorders in Parkinson disease
Dr Niemann: So, not to state the obvious necessarily, but PD is obviously quite a common condition. In fact, it's the second most common neurodegenerative condition after Alzheimer disease. We think of PD many times as a motor disorder because symptoms such as posture, resting tremor, and slowness are quite visible. But there's a whole array of very common and often problematic nonmotor symptoms. That includes not only depression, sleep disorders, constipation, loss of sense of smell, but also skin disorders. And the reason that PD presents with this broad range of symptoms is because it's not just a disorder of the brain itself. It's a multisystem disorder; it affects pretty much the whole body.
There are certain disorders that occur more common in PD than you would expect by chance. In terms of skin, this would be things like changes in sweating, seborrheic dermatitis, melanoma, something called bullous pemphigoid, rosacea, and other conditions. I think the main ones that seem to arise prior to PD are probably changes in sweating. We know that before someone presents with motor features of PD, they can have alterations of the autonomic nervous system, and that can lead to changes in sweat patterns.
Seborrheic dermatitis, which is another common condition that's characterized by redness, scaling, oiliness, sometimes burning pain in the seborrheic areas of the body—so the scalp, the eyebrows, nasolabial folds, the chest sometimes—can also in part be due to autonomic dysfunction, but likely also because of other things such as reduced facial expression or reduced facial movements, changes in hygiene, changes in lipid composition, and changes in the fungi that are on the skin.
Then there's another group of disorders that have perhaps more, or greater, morbidity and where the relationship is much more complex. The main one that people often think of in that regard is melanoma. We've known for several decades now that there is an increased risk of melanoma in PD. There was a recent paper that we referenced in our review article, which was a study done on North American populations in which the risk of melanoma seemed to be 2-and-a half–fold greater for people with PD compared with those without.
The exact reason for the association is not completely established, but things like risk factors are shared between PD and melanoma. So, Caucasian race, fair skin, red hair, male gender, pesticide exposure, etc, all increase the risk of both PD and melanoma. There are genes that cause PD that are also found to be mutated in certain melanomas—so there's that correlation. There are genes that control melanin synthesis that in parts are pigmentation that can affect your risk of melanomas, but also affect your risk of PD. And then there's also imaging features that are shared between PD and melanoma.
In particular, I’m referring to the appearance of the midbrain, which is a structure that's involved in PD. When that structure is evaluated using ultrasound, a so-called hyperechogenic area can be visualized, and that can be seen in PD. It can be used as a biomarker of PD, but actually a lot of people with melanomas, even without PD, can also have similar imaging changes. So that's very interesting.
Lastly, on that note, I'll just mention that there have been reports and concerns, in the past primarily, that levodopa, which is the primary treatment for PD. might increase the risk of melanoma. The reason for that suspicion has been that levodopa is both a precursor to dopamine, which treats PD, but it's also a precursor to melanin, which is found in our skin and melanomas, etc. Several high-level studies, high-quality studies have firmly refuted that there's any association between use of levodopa and development of melanoma.
I won't go into much more detail, but there's also a couple other conditions that are a little bit less common, such as rosacea and bullous pemphigoid, that can also be seen more common in PD.