Definition
Neurocutaneous melanosis (Melanosis neurocutanea), also known as neurocutaneous melanoblastosis syndrome or neurocutaneous melanocytosis, is a rare skin disease in which the brain and parts of the spinal cord can also be affected. The disease is congenital, but is not inherited (not hereditary). The symptoms are usually developed by the end of the first years of life. Typical for neurocutaneous melanosis are the numerous, sometimes oversized moles that are located all over the body.
Causes of neurocutaneous melanosis
The exact mechanisms of disease development are not yet fully understood. However, the cause is suspected to be a so-called neuroectodermal dysplasia. This means that cells from the neuroectoderm develop atypically (dysplastically) during embryonic development. The neuroectoderm is a structure in the embryo from which the central nervous system (brain and spinal cord) and the peripheral nervous system (all nerves outside the brain and spinal cord) later develop. Melanocytes, the pigment-forming cells of the skin, also emerge from the neuroectoderm and abnormal growth of these cells is suspected to be the cause of the disease.
Diagnosis/MRI
The diagnosis of neurocutaneous melanocytosis is based on a physical examination. Numerous large or oversized moles on the head, trunk and extremities are characteristic of the disease. After the diagnosis is made, magnetic resonance imaging (MRI) must be used to determine whether neurological damage is also present. A neurologist or neuroradiologist evaluates the images of the brain and spinal cord and then diagnoses either asymptomatic (without neurological involvement) or symptomatic (with neurological involvement) neurocutaneous melanocytosis. This may also be of interest to you: Procedure of an MRT
Associated symptoms
The main feature of neurocutaneous melanocytosis is the large liver spots, also known as nevus, which are an accumulation of melanocytes, the pigment-producing cells of the skin. Usually these moles become very large (large-area giant pigment nevi) and occur in combination with many smaller moles, which may also be hairy. The diameter of individual giant pigment nevi can range from 20 cm (“large”) to 40 cm (“oversized”) in adults.
In newborns the size of the moles is between 6-9 cm. The spots are found on the whole body, especially on the head, neck, back, buttocks and in the abdominal area. In most cases, neurocutaneous melanocytosis is asymptomatic, i.e. in this case without involvement of neurological structures.
If neurological involvement is present, nevus melanocytes also accumulate in the central nervous system. In such cases, clinical symptoms occur, including headaches, seizures, vomiting, visual disturbances, movement disorders and paralysis. In case of neurological involvement, there is a risk of developing a tumor of the connective tissue in the meninges (leptomeningeal melanoma) or brain maldevelopment (e.g. hydrocephalus internus).
