What is hypertrichosis?
Hypertrichosis is excessive hair growth over and above the normal for the age, sex and race of an individual, in contrast to hirsutism, which is excess hair growth in women following a male distribution pattern. Hypertrichosis can develop all over the body or can be isolated to small patches.
Hypertrichosis may be congenital (present at birth) or acquired (arises later in life).
What causes hypertrichosis?
The cause of hypertrichosis is unknown. Congenital hypertrichosis is believed to be a genetic disorder that is inherited or occurs as a result of spontaneous mutation. Acquired hypertrichosis lanuginosa sometimes occurs in people who at a later stage are diagnosed with a cancer of some form. This hair growth, also known as malignant down, is often confined to the face with long fine silky hair noticeable on the nose and eyelids, sites that are normally hairless. It is not known why a cancer causes this excessive hair growth.
Generalised acquired hypertrichosis may be associated with:
- Porphyria cutanea tarda
- Malnutrition, eg anorexia nervosa
- Drug, eg ciclosporin, phenytoin, androgenic steroids, minoxidil
Localised acquired hypertrichosis may be associated with:
- Increased vascularity
- Repetitive rubbing or scratching (lichen simplex)
- Application of plaster cast (temporary)
- Repeated application of minoxidil, potent topical steroid, iodine, psoralens (topical PUVA)
- Trichomegaly (long eyelashes) can arise from local bimatoprost or systemic erlotinib
Clinical features of congenital hypertrichosis
Congenital hypertrichosis lanuginosa
This is a very rare syndrome with only about 50 cases reported worldwide since the Middle Ages. The condition is characterised by excessive hair growth on a child at birth. Most of the body is covered with lanugo hair, which is an unpigmented, fine, soft and silky hair that covers the fetus and which is usually shed at around 8 months gestation and replaced with fine vellus hair and terminal scalp hair in preparation for birth. In congenital hypertrichosis, lanugo hair continues to grow and this excessively long fine hair persists throughout life.
Congenital hypertrichosis terminalis
This is a variation of congenital hypertrichosis. This condition involves all over body hair growth, but the hair is fully pigmented terminal hair and the condition is almost always associated with gingival hyperplasia (teeth defects). People with congenital hypertrichosis are often referred to as
ape-men and back in the 19th century and perhaps even today, are crowd-drawers at sideshow acts.
This is an unusual form of hypertrichosis where a solitary circumscribed area of terminal hair growth occurs. It is not usually associated with any other diseases, except if it arises as a
faun-tail on the lower back, when it may indicate underlying spina bifida. Naevoid hypertrichosis can occur at birth or appear later in life. An example of naevoid circumscribed hypertrichosis is the presence of a solitary and very bushy eyebrow.
Hypertrichosis associated with other naevi
Clinical features of acquired hypertrichosis
Acquired hypertrichosi describes excess hair growth that develops in an individual after birth. The hair is usually unpigmented vellus hair or may involve pigmented terminal hair. Excess hair growth may be localised to a particular area or generalised and covering all hair-bearing areas of the body.
What is the treatment for hypertrichosis?
Treatment of hypertrichosis is basically hair removal. Several methods are available but need to be repeated regularly as hair continues to grow back. They may also cause scarring, dermatitis or hypersensitivity reactions.
More recently, laser hair removal has been proposed as a treatment option. It appears to have fewer side effects and produces a longer lasting result.