Author: Hon Assoc Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 2010.
An epidermal naevus is a type of birthmark in which there is an overgrowth of one or more components of the epidermis or outer layer of skin. Epidermal naevus syndromes refer to the co-existence of an epidermal naevus with other abnormalities in the skin and other organs. They are sometimes called systemitised epidermal naevi. They reflect mosaicism, in which there are two distinct cell lines with differing genetics.
Epidermal naevus syndromes usually arise sporadically, with rare reports of familial cases. Some of the syndromes are now well defined. The molecular / genetic basis is under investigation.
Naevus sebaceous or organoid naevus is a type of epidermal naevus in which there is overgrowth of sebaceous glands and/or hair follicles. It is a component of several syndromes.
Schimmelpenning syndrome has two Online Mendelian in Man entries (OMIM 163200, 601359). Its other names include:
Phacomatosis pigmentokeratotica is an example of didymosis (twin spotting) because two distinct syndromes appear to overlap in one person. It is characterised by:
Problems associated with phacomatosis pigmentokeratotica include features associated with Schimmelpenning syndrome (above) and with papular naevus spilus syndrome. These are:
Many other abnormalities have been described in individual cases.
Didymosis aplasticosebacea is the association of sebaceous naevus with aplasia cutis congenita.
SCALP syndrome is didymosis aplasticosebacea in association with a giant melanocytic naevus: Sebaceous naevus, Central nervous system abnormalities, Aplasia cutis, Limbal dermoid and Pigmented naevus.
The comedone naevus is composed of a group of blocked hair follicles i.e. blackheads. They are often pitted. It has sometimes been reported in association with other defects.
Various other features have been described in individual cases.
These are the angora hair naevus syndrome and Becker naevus syndrome.
The Angora hair naevus is an epidermal naevus covered with long soft white hair. The syndrome may also include:
The Becker naevus presents as darkened skin patches, often with a map-like or checkerboard outline. It is most commonly found on the upper back or shoulders. It tends to be more prominent in males because of the growth of dark hair within it at puberty. The syndrome may also include:
These include Proteus syndrome, Type 2 segmental Cowden disease and CHILD syndrome.
Proteus syndrome is characterised by overgrowth of skin, connective tissue, fat, bones and other tissues.
Multiple hamartoma syndrome or Cowden disease can include a Cowden naevus, when it is called Type 2 segmental Cowden disease. The Cowden naevus is a linear thick, bumpy, wart-like growth. PTEN (phosphatase and tensin homologue) gene mutations have been detected, which are not present in Proteus syndrome, which type 2 segmental Cowden syndrome may resemble. The PTEN gene's normal function is to suppress tumours. The features of Type 2 segmental Cowden disease include:
CHILD syndrome is inherited as an X-linked dominant disorder, and is lethal in males. CHILD stands for Congenital Hypoplasia with Ichthyosiform naevus and Limb defects. It is due to mutations in the gene known as NSDHL (or NAD[P]H steroid dehydrogenase-like gene). This gene involved in the metabolism of cholesterol.
The CHILD naevus is variable, inflamed and covered by waxy yellowish scales. It is usually either strictly on one side of the body (most often the right) with clear-cut midline demarcation, or it may follow Blaschko lines, or both. It often favours a body fold. Pathology characteristically shows foamy histiocytes in the dermal papillae. CHILD naevus can spontaneous disappear only to reappear later.
Other features may include:
There are numerous individual case reports or small series of cases that do not fit into the descriptions above. Some of these have been given names:
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