Epidermal naevus syndromes
What are epidermal naevus syndromes?
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.
Syndromes associated with sebaceous naevus
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:
- Schimmelpenning-Feuerstein-Mims syndrome
- SFM syndrome
- Linear sebaceous naevus syndrome
- Jadassohn naevus phakomatosis
- Naevus sebaceus of jadassohn
- Organoid naevus phakomatosis
- Sebaceous naevus – which may have minimal sebaceous overgrowth
- Skeletal defects – deformities of face, trunk and limbs
- Ocular defects – conjunctival or corneal growth or coloboma
- Cerebral defects – mental deficiency, seizures, enlarged or shrunken brain tissue
- Hypophosphataemic rickets – vitamin d deficient bone disease
Phacomatosis pigmentokeratotica is an example of didymosis (twin spotting) because two distinct syndromes appear to overlap in one person. It is characterised by:
- Sebaceous naevus
- Papular naevus spilus (speckled lentiginous naevus)
Problems associated with phacomatosis pigmentokeratotica include features associated with Schimmelpenning syndrome (above) and with papular naevus spilus syndrome. These are:
- Hyperhidrosis (excessive sweating)
- Muscular weakness
- Dysaesthsia (sensory disturbance)
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.
Syndrome associated with comedone 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.
- Cataract on the same side as the naevus
- Bone defects on the same or opposite side
- Neurological defects on the same or opposite side
Various other features have been described in individual cases.
Syndromes associated with excessive hair growth
These are the angora hair naevus syndrome and Becker naevus syndrome.
Angora hair naevus syndrome
The Angora hair naevus is an epidermal naevus covered with long soft white hair. The syndrome may also include:
- Neurological defects – such as mental retardation, seizures, spasticity
- Skeletal defects – mainly facial malformations
Becker naevus syndrome
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:
- Poor breast or nipple development on the affected side – more obvious in females
- Supernumerary nipples
- Loss of subcutaneous fat
- Musculoskeletal abnormalities and asymmetry
Syndromes associated with keratinocytic epidermal naevi
These include Proteus syndrome, Type 2 segmental Cowden disease and CHILD syndrome.
Keratinocytic epidermal naevus
Proteus syndrome is characterised by overgrowth of skin, connective tissue, fat, bones and other tissues.
- Soft, velvety, flat epidermal naevus in 50% of cases
- Other naevi, e.g., vascular malformation, lymphatic malformation, cutis aplasia, lipomas
- Brain-like (cerebriform) overgrowth of palms or soles
- Enlarged finger(s) or toe(s)
- Overgrowth of any other bone or tissue
- Neurological defects including mild mental deficiency and seizures
Type 2 segmental Cowden disease
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:
- Linear Cowden naevus
- Other naevi, e.g., vascular malformation, lymphatic malformation, lipomas
- Neurological defects including hydrocephalus, seizures
- Overgrowth of limbs and toes
- Jejunal or colonic polyps
CHILD syndrome is inherited as an X-linked dominant disorder, and is lethal in males. CHILD stands for CongenitalHypoplasia 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:
- Thickened abnormal nails
- Strawberry-like lesions on the tips of finger(s) or toe(s)
- Skeletal defects – shortened or absence finger(s) or limb(s)
- Long bone Xray changes – chondrodysplasia punctata
- Undergrowth of other bones
- Congenital heart, kidney or other organ defects
- Neurological diseases
Other epidermal naevus syndromes
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:
- Fibroblast growth factor receptor 3 (FGFR3) epidermal naevus syndrome (García-Hafner-Happle syndrome) caused by a mosaic R248C mutation of the FGFR3 Gene
- Naevus trichilemmocysticus syndrome
- Gobello syndrome: epidermal naevus characterised by hypertrichosis and follicular herpkeratosis in association with multiple bone defects.
- NEVADA syndrome: Naevus Epidermicus Verrucosus with AngioDysplasia and Aneurysms
- CLOVE syndrome: Congenital Lipomatous Overgrowth, Vascular malformations and Epidermal naevus (similar but distinct from Proteus syndrome)