Hypertrichosis or werewolf syndrome is the presence of excessive and abnormal hair (lanugo, villous or terminal) in places on the body or face that do not usually present it. Lanugo is a thin, fine hair that already appears on the fetus and disappears at the end of pregnancy or during the first months of the baby’s life. The hair or vellus hairs are short and are produced by hair follicles that penetrate the papillary dermis. Finally, terminal hairs are formed by hair follicles that penetrate to the reticular dermis; They are big, they have color and pith.
Hypertrichosis is a rare disease and aesthetic problem that is usually hereditary although it does not pose a health risk. It can also appear due to acquired causes or be a cutaneous manifestation of a systemic disease. It can be localized but in its most extreme forms it is generalized except in the palms of the hands and soles of the feet.
The causes of hypertrichosis are very varied and the pathophysiology is an enigma. The main mechanisms of hypertrichosis are three: the conversion of hair into terminal hair, changes in the hair growth cycle or increase in the density of hair follicles.
The classification of hypertrichosis is:
– Congenital hypertrichosis (localized and generalized). Localized congenital hypertrichosis are: congenital nevus, smooth muscle hamartoma, nevoid hypertrichosis, neurofibromas, ulnar hypertrichosis (hairy elbows), hemihypertrophy, hairy skin malformations on palms and soles, hypertrichosis of the pinna, spinal dysraphism and anterior cervical hypertrichosis.
– Generalized congenital hypertrichosis is divided into syndromes with hypertrichosis as a primary manifestation or as a secondary manifestation.
– Generalized hypertrichosis as a primary manifestation: Congenital hypertrichosis lanuginosa (CHL), Ambras syndrome, congenital generalized or X-linked hypertrichosis, gingival fibromatosis and osteochondrodysplasia,
– Generalized hypertrichosis as a secondary manifestation: Brachman-de Lande syndrome, teratogen syndromes, lipoatrophy (such as lipoatrophic diabetes), mucopolysaccharidosis, Winchester syndrome, porphyrias, Rubinstein-Taybi syndrome, Coffin-Siris syndrome, hemimaxillofacial dysplasia, Craniofacial dysostosis, hypomelanosis of itus and MELAS syndrome.
– Acquired hypertrichosis (localized and generalized). Localized acquired hypertrichosis are: Becker’s nevus, hypertrichosis associated with local inflammation, hypertrichosis of the auricle and trichomegaly.
– Generalized acquired hypertrichosis is: due to brain disorders such as postviral encephalitis, chronic exposure to mercury (acrodynia), infections such as tuberculosis that can cause transient hypertrichosis in children, malnutrition, dermatomyositis, hyperthyroidism or hypothyroidism, Lawrence-Seip syndrome, porphyrias acquired, acquired hypertrichosis lanuginosa that is associated with lung and colon neoplasms, POEMS syndrome, and pharmacological hypertrichosis such as that produced by latanoprost in the treatment of glaucoma.
The sign of the appearance of hypertrichosis is the growth of hair in areas where it is not usual. Below we note the symptoms or types of growth depending on the type of hypertrichosis.
– In congenital nevus, hair grows inside the lesion.
– Smooth muscle hamartoma is a hyperpigmented plaque or tumor with a “cobblestone” appearance; It predominates in the trunk with hypertrichosis.
– Nevoid hypertrichosis is the increase in the number of normal hair follicles in a congenital plate of terminal hair.
– Hypertrichosis associated with soft tumors in or under the skin (neurofibromas) involves hypertrichosis and hyperpigmentation in neurofibroma.
– Ulnar hypertrichosis (hairy elbows) is excessive hair growth bilaterally. It generally appears in infancy, develops during childhood, and resolves partially or completely during adolescence.
– Hemihypertrophy is the growth of terminal hair on half of the body or only part. There may be abnormal nail growth, an increase in hair diameter and the number of terminal hair follicles where there are normally hair follicles.
– Hairy skin malformation of palms and soles. It has an autosomal dominant inheritance pattern. It’s very rare.
– Spinal hypertrichosis presents excess hair in the spinal region or “faun’s tail”, or as vellus hair in the midline.
– Anterior cervical hypertrichosis is a small area of terminal hair located on the Adam’s apple.
– Congenital hypertrichosis lanuginosa (CHL) is lanugo that remains throughout the body except the palms, soles and mucous membranes after birth.
– Ambra syndrome is abundant hairy hair on the face, ears and shoulders whose density does not decrease with age. There may be facial and dental dysmorphia.
– Generalized or X-linked congenital hypertrichosis. Only one family has been reported in Mexico with an X-linked recessive inheritance pattern, so males are more affected than females. The affected gene is X24-q27.1. There is congenital terminal hypertrichosis of the face, trunk and extremities, sparing the palms, soles and mucous membranes.
– Osteochondrodysplasia associated with hypertrichosis is an autosomal recessive syndrome that can present a large fetus (macrosomia) and a dilated heart (cardiomegaly) in children.
– Brachman-de Lande syndrome. It is characterized by thick and converging eyebrows, hypertrichosis of the eyelashes, low hair growth and a low forehead covered with downy hair. Other characteristics are: mental retardation, depressed nasal bridge, low set ear pinnae, developmental abnormalities of arms and feet, or small and irregular teeth.
– Teratogenic syndromes that include: hypertrichosis, nail hypoplasia, cleft lip and palate, mid-facial hypoplasia, upper lip hyperplasia and low birth weight.
– Lipoatrophy includes acanthosis nigricans, excessive sweating (hyperhidrosis), prominent veins (phlebomegaly), accumulations of fat that harden (xanthomas) and hypertrichosis of the face, neck and extremities.
– Mucopolysaccharidoses that are characterized by short stature, skeletal abnormalities, enlargement of the liver and spleen (hepatosplenomegaly) and cardiac abnormalities.
– The syndrome of stiff skin or “stone-like” skin. Excess hair growth is mild and occurs in half of the cases.
– Winchester syndrome is distinguished by thick skin with hypertrichosis, short stature, severe bone tissue destruction in the carpal and tarsal bones, and corneal opacity.
– Porphyrias that present photosensitivity of the skin with blisters, scars, and hypertrichosis in areas exposed to the sun.
– Rubinstein-Taybi syndrome, which is characterized by a “little bird” face, raised and pink scars (keloids), large fingers and toes, short stature and mental retardation.
– Schinzel-Giedion syndrome presents hypertrichosis of the face and extremities, accompanied by a depressed nasal bridge, broad forehead, facial hypoplasia, dental and skeletal alterations.
– Barber-Say syndrome is characterized by atrophic skin with hypertrichosis on the forehead, neck, trunk and extremities, facial fissure (macrostomia), mental retardation and excessive tearing (ectropion).
– Coffin-Siris syndrome presents with lumbosacral and eyebrow hypertrichosis, absence of fingers and toes, mental and growth retardation, sparse hair on the scalp, joint laxity, microcephaly, prominent lips and a depressed nasal bridge.
– In hemimaxillofacial dysplasia there is facial asymmetry, the upper part of the jaw is enlarged on one side and occasionally facial hypertrichosis on only one side.
– Craniofacial dysostosis presents hypertrichosis of terminal hair predominating in the trunk and extremities with hypoplasia of the labia majora, and dental and ocular abnormalities.
– Ito hypomelanosis is characterized by hypopigmented spots that follow Blaschko’s lines (skin lines that are not seen under normal conditions). There may be neurological manifestations.
– MELAS syndrome presents dermatological manifestations that include pruritic erythema on the neck and hypertrichosis of terminal hair on the feet.
– Becker’s nevus is an irregularly pigmented tumor (hamartoma) with increased hair growth inside that predominates on the trunk during puberty. It is generally acquired, is more common in men and occurs solitary and unilaterally.
– Hypertrichosis associated with local inflammation appears due to the use of chemicals such as iodine. Excessive hair is temporary and disappears after a few months.
– Hypertrichosis of the auricle predominates in elderly men, patients with HIV, children of diabetic mothers and diabetic patients.
– Trichomegaly is the isolated alteration of the eyelashes.
– Acrodynia is characterized by erythema of the fingers, toes and nose, excessive perspiration and salivation, and pain in the feet and hands. There are cases with the presence of hypertrichosis.
– Tuberculosis can cause transient hypertrichosis in children, with predominance of hair on the face and extremities.
– Juvenile dermatomyositis presents hypertrichosis of the face and extremities.
– In cases of hypothyroidism, hypertrichosis is common in children and disappears with replacement therapy. In patients with hyperthyroidism, hypertrichosis has been reported in cases of myxedema, a type of pretibial edema due to the accumulation of long chains of sugar molecules (mucopolysaccharides).
– Lawrence-Seip syndrome, which can appear after a viral infection, causes loss of subcutaneous fat, hyperinsulinemic diabetes, acanthosis nigricans and hypertrichosis.
– Hypertrichosis can occur in acquired porphyrias such as porphyria cutanea Tarda, which can be caused by exposure to substances such as hexachlorobenzene, a pesticide.
– In acquired hypertrichosis lanuginosa there is regression of normal hair follicles to lanugo hair that predominates on the face.
– In POEMS syndrome, skin changes include hyperpigmentation, generalized hypertrichosis although predominant in the lower extremities, skin thickening, edema, and flat, raised spots (cutaneous angiomas).
– Pharmacological hypertrichosis appears when following pharmacological treatment and predominates in the trunk and extremities; rarely the face.
In addition to the physical examination and the description of symptoms, the specialist will request blood tests to determine hormonal levels and imaging tests such as ultrasounds and/or computed tomography scans to detect tumors or other disorders that may be the cause of abnormal hair growth.
If hypertrichosis appears due to a triggering factor, the goal is to treat the disease or cause. When it is primary, the options are reduced to hair makeup, bleaching, and hair removal methods, among which the laser hair removal technique or permanent hair removal that manages to destroy the germ cells of the hair stands out.
No preventive measures against hypertrichosis have been described.