Friday, December 26

Congenital hypertrichosis

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What is congenital hypertrichosis?
Hypertrichosis is the excessive growth of hair over the body. Congenital hypertrichosis (CH) is the presence of excessive hair growth at birth.
Congenital hypertrichosis may be present as an inherited genetic disorder. Congenital hypertrichosis may also occur as a result of spontaneous mutation during fetal growth. CH may concur and coexist with many hereditary medical conditions.

Types of congenital hypertrichosis

The excessive growth of hair is classified as congenital hypotrichosis when it is present at birth. Acquired hypotrichosis is the appearance of excessive hair growth later in the life. CH may involve terminal, Vellus or lanugo hair. CH may be generalised covering the entire body or localized and circumscribed. Some of the many forms of congenital hypertrichosis are discussed below.

Generalized congenital hypertrichosis (GCH)

Various types of genetic inheritance and spontaneous mutation can cause GCH. The entire body may be covered sparing, mucous membranes, palms and soles. The excessive growth of hair may involve either terminal hair or lanugo hair.

Congenital hypertrichosis lanuginosa (CHL)

In congenital hypertrichosis lanuginosa, the entire body of the newborn is covered by the lanugo hair.
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Only the mucous membranes, palms, soles, dorsal terminal phalanges, labia minora, prepuce, and glans penis are spared. The CHL may occur as an autosomal dominant inheritance or as a sporadic mutation. It is believed that mutations of gene in 8q22 of chromosome 8 is the cause.

Ambras Syndrome is an extremely rare type of congenital hypertrichosis lanuginosa, characterized by the vellus-type hair covering the entire body. Abnormalities like dental anomalies, triangular, coarse face, bulbous nasal tip, delayed tooth eruption, absence of teeth, glaucoma, pyloric stenosis, photophobia are associated with Ambras syndrome.

X-linked generalized congenital hypertrichosis (X-GCH)

X-GCH occurs very rarely. The excessive terminal hair growth was mapped to chromosome Xq24-q27.1 in a Mexican family. Terminal hair covers the face, trunk and limbs, sparing mucosa, soles and palms. It may be associated with medical conditions such as, gingival hyperplasia, scoliosis, and spina bifida.

Cornelia de Lange Syndrome (CDLS)

CDLS is a genetic disorder present from birth. The disorder can occur due to mutation in genes NIPBL, SMC1A or SMC3. The disorder is characterized by thick and convergent eyebrows (synophrys), thick and long eyelashes, and low hairline. Vellus hair hypertrichosis of trunk, posterior neck, sacrum and elbows is seen. It may be associated with abnormalities such as cutis marmorata, upturned nostrils, depressed nasal bridge, low set ears, small and irregular teeth, high palate and bifid uvula. The patients may have short and abnormal arms, hands and feet. They may suffer from severe mental retardation.

Localized congenital hypertrichosis

Congenital localized hypertrichosis is a notable feature of congenital melanocytic nevus, congenital Becker nevus, Hypertrichosis cubiti, smooth muscle hamartoma and nevoid hypertrichosis. The localized abnormal hair growth may be at a single site or just a few sites.

Congenital melanocytic nevus (CMN)

Congenital melanocytic nevus (CMN) is a type of melanocytic nevus found in newborns. CMN is usually larger than the acquired melanocytic nevus. The lesion may be covered by excessive growth of terminal hair. There are three types of CMN. Small-sized congenital nevocytic nevus has a diameter less than 2 cm. Medium-sized CMN has a diameter more than 2 cm but less than 20 cm. Nevus pigmentosus et pilosus (giant nevus) is more than 20 cm in diameter with dark pigment and terminal hypertrichosis.

In about 2% to 45% of patients with giant melanocytic nevi at birth, neurocutaneous melanosis is involved. Neurocutaneous melanosis (NCM) is characterized by melanocytic nevi on the skin and melanocytic tumors in the leptomeninges of the central nervous system. Nearly half of the patients with neurocutaneous melanosis may develop malignancy in the form of leptomeningeal melanoma. Early embryonic, postzygotic somatic mutations in the NRAS gene are implicated in the pathogenesis of NCM.

Hypertrichosis cubiti

Hypertrichosis cubiti, also known as hairy elbows syndrome, is a rare symmetric, localized, congenital, circumscribed hypertrichosis with long vellus hair occurring on the elbow (extensor surfaces). Both familial and sporadic forms have been reported. Partial or complete resolution during puberty is reported. A very high percentage of hair in the elbow appear to be in the anagen phase.

The hairy elbows syndrome may in some cases have associated abnormalities. Short stature or other physical abnormalities such as dysmorphic facial features, microcephaly, joint hyperlaxity, thin-long-webbed neck and mental retardation have been associated with hypertrichosis cubiti. Autosomal dominant as well as autosomal recessive inheritance is postulated in the pathogenesis.

Congenital smooth muscle hamartoma

Smooth muscle hamartomas are caused by the benign proliferation of smooth muscle bundle within the dermis. It is an uncommon malformation of the pilar smooth muscle, often involving the back and lower limbs. These lesions typically appear as a skin colored or lightly pigmented patch or plaque with hypertrichosis of vellus hair.

Becker's nevus

Becker's nevus is due to an overgrowth of the epidermis, melanocytes and hair follicles. Though most often it is seen as an acquired disorder with terminal hypertrichosis, it may also be present at birth. The pathophysiology of Becker's nevus remains unclear. A case was reported wherein the disorder had genetic association. A 16 month boy had a lesion on his right shoulder and a similar lesion existed on the right shoulder of his father.

Nevoid Hypertrichosis

Nevoid Hypertrichosis usually appears as a solitary patch of terminal hair without other abnormalities anywhere in the body. If present in lumbosacral area, differential diagnosis is required to rule out faun tail deformity conditions like, spina bifida occulta and diastematomyelia.

Lumbosacral hypertrichosis

Lumbosacral hypertrichosis is also known as faun tail deformity. This malformation is associated with cutaneous anomalies such as sacral dimple, lipoma, port-wine stain, hypertrichosis or dermoid cyst. It is also associated with bone and spinal cord defects such as spina bifida occulta, diastematomyelia, myelomeningocele, and vertebral abnormalities.

Hairy palms and soles

Hairy palms and soles is a bilaterally symmetric, hereditary hypertrichosis affecting the palms and soles. It is an autosomal dominant inheritance. The hair follicles are normal and the children and women have vellus hair. The excessive hair growth is androgen-sensitive and in boys the vellus hair becomes terminal at puberty.

Anterior cervical hypertrichosis

The cause of this congenital disorder can be autosomal dominant, autosomal recessive or X-linked chromosomal mutations. Excessive hair growth is observed on the neck of the affected individuals. In the autosomal recessive mutation, peripheral neuropathy is observed.
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Reference:
1.Trüeb RM. Causes and management of hypertrichosis. Am J Clin Dermatol. 2002;3(9):617-27.
2.Goel N, Rajaram S, Gupta B, Gupta K. Familial congenital generalized hypertrichosis. Indian J Dermatol Venereol Leprol 2013;79:849.
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