Types of Hypertrichosis

Congenital Hypertrichosis Lanuginosa (CHL):

This is a very rare inherited disorder with about 50 cases reported worldwide since the Middle Ages. In earlier times, the patients were considered an exotic "species", much prized for their curiosity value. At birth, the long and silky lanugo hairs, normally shed before or shortly after birth, remain on the infant’s entire body, sparing only the palms and soles. The growth is typically more on the face, ears and shoulders. In the documented cases, no reduction in hair growth was seen later in life.

A variant of generalized congenital hypertrichosis is congenital hypertrichosis lanuginosa (CHL) where the hair is fine, blond, lanugo type hair. The patients are normal except for abnormal dental eruptions. The hypertrichosis may persist, decrease or increase with age. Brachmann de Lange is a variant of CHL where the growth is less generalized and the infants have a particular appearance due to associated mental and growth retardation. Hair shedding begins in the first year of life starting at the trunk and progressing to the limbs.

Generalized Acquired Hypertrichosis:

Acquired generalized hypertrichosis is commonly caused by drugs like phenytoin, cyclosporine A, and minoxidil among others. Hypertrichosis disappears once the drug intake is discontinued. The time taken depends on the growth site and is usually 3 months to a year. Less commonly, hypertrichosis is caused by head injuries, malnutrition, starvation and AIDS.

Generalized hypertrichosis is also caused by a class of disorders known as porphyries, which are often triggered by exposure to chemicals of which hexachlorobenzene is a common example. Excess growth tends to disappear once exposure ceases.

Localized Congenital Hypertrichosis:

Localized hypertrichosis here is restricted to a single or just a few sites such as the back, elbows, ears and nevi. Excess hair on the back can be a sign of underlying neural abnormalities or spinal defects. Therefore, early daignosis treatment is critically important.

Excess hairs on the elbows are termed hypertrichosis cubiti. The growth becomes more prominent in early childhood and usually disappears partially or fully in adolescence.

Hairy pinna is excessive hair on the ears and is more common among older men. In babies, it can be associated with a diabetic mother. AIDS patients and diabetic patients can also have excess hair on their ears.

Hairy nevi are the most common hypertrichosis among babies. Additionally the nevi are often pigmented. It is usually not anindicator of any underlying abnormality.

Localized Acquired Hypertrichosis:

These are transient hypertrichoses caused by a variety of injuries like trauma, irritation or inflammation, which transform vellus hairs into coarse terminal hairs as a repsonse to the local injury.

Becker’s nevus is a common disorder where sunburn or other injuries to the shoulder cause excess hair growth and pigmentation of the site. It heals with time and is more common among men. The application of plaster casts for broken bones often causes excess hair growth underneath the cast. AIDS is known to cause excess hair growth of the eyelashes, a disorder called trichomegaly.

Naevoid Hypertrichosis:

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.