Defining hypertrichosis and its distinction from hirsutism
Information on hypertrichosis and hair removal treatments
What is Hypertrichosis ?
Though hypertrichosis is mainly a cosmetic problem, it is sometimes an indicator
of underlying systemic problems and can be used as a diagnostic tool.
The disorder involves lanugo, vellus and terminal hairs. Lanugo hairs are long silky and un-pigmented and normally appear on the fetus during the third to the seventh month of pregnancy, covering it entirely. The lanugo hair is shed in the seventh or eighth month of pregnancy and replaced by un-pigmented or lightly pigmented vellus hair on the body and pigmented terminal hair on the scalp. Vellus hair grows up to one centimeter at most. The diameter of terminal hair is twice that of vellus and the length is at least, and usually more than, 2 centimeters.
It should be noted that individual hairs, even in adulthood, can express any of these three types of hair and can change from one to the other.
In this article the classification of hypertrichosis as is essentially classified as generalized or localized, but classification can also be based on age of onset and site of growth.
The generalized type of hypertrichosis can involve all three types of hair (lanugo, vellus, terminal) while localized hypertrichosis almost always involves terminal hair growth.
These types of hypertrichosis are further sub-divided into congenital and acquired hypertrichoses.
Congenital: In universal congenital hypertrichosis the whole body, except areas where hair normally does not grow, is covered with a large amount of lanugo hair. Only the scalp hair, eyebrows and eyelashes are darker. Hair growth is more prominent on the face, ears and shoulders. In none of the known cases was there any decrease of hair later.
In congenital hypertrichosis lanuginose, excessive hair at birth or early infancy may cover the entire body except the hands and feet. Patients are normal except for dental eruptions. Hair is shed gradually from the first year of life.
In Bachmann de Lange variant the affected infants can be easily recognized
from their characteristic and stable appearance, which includes distinctive
faces, low to secondary hairline, penciled but not bushy eyebrows, long eyelashes
and thin lips. They also have constant abnormalities such as mental and growth
Acquired: Acquired hypertrichosis, particularly drug induced, is more common than other kinds of generalized hypertrichosis. It is mostly vellus hair and rarely lanugo.
Cancer can cause hypertrichosa. Hair growth becomes normal after the affected
part is surgically removed. Patients with systemic diseases like porphyra
and POEM also exhibit hypertrichosia. Patients with eating disorders like
bulimia and anorexia nervosa often have lanugo like hypertrichosia.
Congenital: Such hypertrichosis appearing on the back, over the spine is of most concern, since it may indicate occult neural abnormalities. Hair on the lower back called “faun tail” may also indicate spinal defects. These defects may not cause problems in infancy but will eventually cause problems later. Normally they are detected in infancy and occur more frequently in females.
Congenital hair on ears in babies indicates XYY syndrome. Congenital hair on baby’s pinna may indicate a diabetic mother, independent of degree of diabetic control. It may also indicate a Y- linked androgen dependant trait.
Excessive growth of eye lashes or eyebrows are found only in adults. However, combination of excessively long eyelashes and eyebrows in children indicates abnormalities such as Brachmann-de Lange.
Congenital smooth muscle hamartomas are characterized by congenital indurated patches, usually pigmented and having focal hypertrichosis. These characteristics diminish with time.
Congenital pigmented hairy nevi are the most common cause of localized hypertrichosis in infants. Surgery is done more to prevent melanoma than for cosmetic reasons.
Acquired: Physical injuries like repeated trauma, irritation and inflammation may lead to transformation of local vellus into terminal hair causing hypertrichosis
Becker’s nevus, a form of hypertrichosis on the upper back, is caused by sunburn. Terminal hairs are sometimes found on the scrotum of children, aged 3 months to two years, which may be due to normal rise in testosterone levels at that age.
Acquired hypertrichosis of eyelashes, eyebrows and ears have been seen in AIDS patients.
Treatment options are limited and depend on the patient characteristics and area and amount of hair growth. Presently there is no cure for congenital hypertrichosis. It is largely some acquired hypertrichosis forms, such as the drug induced ones, which can be successfully and permanently cured by treating the underlying medical problem.
Most common are cosmetic treatments like shaving, plucking, epilation, chemical depilation, electrolysis and laser application, but they are only half measures. Of these only electrolysis and laser treatment are, at present, the best and hold promise of being permanent hair removers in the future.