What is "phakomatosis"

n. Any of a group of neurocutaneous disorders of the central nervous system causing lesions on the skin and eye.

Phakomatoses (or neuro-oculo-cutaneous syndromes, neurocutaneous disorders) are multisystem disorders that have characteristic central nervous system, ocular, and cutaneous lesions of variable severity. The skin and the brain have a common ectodermal origin, so there are many genetic and acquired diseases that affect both tissues. However, in some conditions, such as von Hippel-Lindau disease, ectodermal presentation is minimal.

The term, from the Greek φακός, phakos, "spot, lens", suffix-(o)ma (-ωμα) and the suffix -osis, also called "Mother's spot" or "Birth mark" was introduced by Jan van der Hoeve in 1920, before the distinct genetic basis of each of these diseases was understood.