A Skin Test to Help Diagnose PARKINSON’S DISEASE
In the early stages, PARKINSON’S DISEASE is difficult to diagnose accurately. There are no laboratory tests of blood or urine to define it and imaging studies such as the Dopamine Transporter or Magnetic Resonance Imaging are not always readily available, nor can they differentiate between other neurological diseases such as Multiple System Atrophy (MSA) or Progressive Supranuclear Palsy (PSP). Finding a biomarker, some substance that will be a reliable, measurable marker of a particular state of the disease that will indicate or predict the onset of PARKINSON’S DISEASE has been elusive but researchers are not giving up easily.
Alpha-synuclein has been the subject of a lot of research in PARKINSON’S DISEASE. It has been found to be one of the defining substances found in many regions in Parkinsonian brains, which unfortunately, can only be measured post mortem. Some studies have found alpha synuclein in other organs, outside of the brain, such as the heart, the digestive tract and even in the skin. It is not yet known if alpha synuclein in these peripheral organs is as destructive as it is in the brain, but it does suggest that PARKINSON’S DISEASE involves multiple organs. Other researchers in many institutions have focused on alpha synuclein found in the skin, and have employed many methods to study it resulting in conflicting results, but still adding to the existing knowledge.
A large consortium of researchers from five different research facilities in Mexico designed a study to examine the skin of people with clinically diagnosed PARKINSON’S DISEASE for the presence of alpha synuclein and to differentiate it from people with atypical PARKINSONISM. They enrolled 67 subjects, 34 with PD and 33 with atypical PD and a non-neurologically affected control group of 20 subjects. The researchers took skin sample biopsies that included three parts: the superficial skin layer called the spinous cell layer, the hair follicles or pilosebaceous unit and the ecrine (sweat producing) glands from all three groups of subjects.
All the samples were specifically stained to look for the presence of alpha synuclein and analyzed with immunohistochemical techniques followed by confocal microscopy and three dimensional imaging techniques. Samples from the control subjects showed there was no alpha synuclein present, but almost 60% of the PD subjects showed a positive presence in their epidermis, but only about 7% of the atypical PD subjects tested positive. In the PD positive group, alpha-synuclein was found in the surface skin, the hair follicle cells and the sweat producing glands. In the atypical PD group, very low amounts were found in the surface skin and hair follicle cells, but none was found in the sweat producing glands.
The investigators feel that this type of testing could be very useful in making the distinction between idiopathic PARKINSON’S DISEASE and atypical Parkinsonisms. Still, they feel that their study involved a limited number of subjects and they would like to see this research repeated with a larger cohort of subjects. The presence of alpha synuclein in the skin regions may well correlate to the changes occurring in the brain due to alpha synuclein, making skin testing a potentially accurate biomarker. It is a minimally invasive testing technique that is safe and affordable making it a practical screening tool to simplify accurate diagnoses.
Rodríguez-Leyva, I., Calderón-Garcidueñas, A. L., Jiménez-Capdeville, M. E., Rentería-Palomo, A. A., Hernandez-Rodriguez, H. G., Valdés-Rodríguez, R., Fuentes-Ahumada, C., Torres-Álvarez, B., Sepúlveda-Saavedra, J., Soto-Domínguez, A., Santoyo, M. E., Rodriguez-Moreno, J. I. and Castanedo-Cázares, J. P. (2014), α-Synuclein inclusions in the skin of Parkinson’s disease and parkinsonism. Annals of Clinical and Translational Neurology, 1: 471–478. doi: 10.1002/acn3.78
Review by Marcia McCall