Friday, December 19

Lanugo hair - Lanugo baby

   ›      ›   Lanugo hair - Lanugo baby.
What is lanugo hair?
Lanugo is the fine, soft and downy hair found on the body of a fetus or newborn baby.
The word lanugo is derived from the Latin word "lana", meaning wool. It is the first hair produced by the fetal hair follicles at about five months of gestation. Lanugo may also appear as a congenital defect in a baby or as an after effect of eating disorders.

The development of fetal lanugo

During fetal development, ectoderm forms the surface epidermis and contributes to different associated skin structures like hair follicles, nails and glands. By the forth month of gestation, cords of ectoderm cells extend into mesoderm forming epithelial columns. These cells give rise to hair follicles, sebaceous and sweat glands. At the same time the melanocyte stem cells, which have neural crest origin move into the base of the follicle forming cord.

During fifth month of gestation, lanugo growth gets initiated at the base of the cord and the lateral outgrowths of the cord give rise to sebaceous glands. The sebaceous glands start producing vernix (vernix caseosa).
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Other ectoderm cords elongate and coil to form the sweat glands. By the sixth month of gestation, the body is fully covered by lanugo and has considerable deposit of vernix caseosa.

The lanugo growth over the entire body is at the same rate and the hairs appear to be of the same length. By the eighth month of gestation, the fetal skin is completely coated with vernix and the lanugo starts disappearing. By the ninth month of pregnancy, most of the embryonic hair is shed. Premature babies born before the complete shedding are seen still covered with embryonic hair.

Sometimes in full term babies also the lanugo is seen which may eventually disappears of its own accord within a few days or weeks. The persisting fine downy hair is completely shed when the baby is three to four months old. It is usually replaced by short, soft and near transparent vellus. It is also interesting to note that babies nearing their term in the womb swallow the lanugo along with amniotic fluid. The meconium (first stool) from newborn babies contains lanugo.
hair development stages

Function of fetal lanugo

Vernix caseosa is the waxy, cheese-like substance secreted by the fetal sebaceous glands to cover the fetal skin. Its secretion starts around 18 weeks into pregnancy and is seen coating the newborn babies. Vernix functions as a protective coating against the watery environment. Lanugo has the important role of binding the vernix to fetal skin.

Lanugo and eating disorders

Lanugo is observed in patients suffering from malnutrition and eating disorders like anorexia nervosa. Anorexia nervosa is characterized by a fierce quest for thinness in addition to having an intense fear of gaining weight. Most of the anorexia nervosa patients are adolescents, especially girls. Excessive preoccupation with body shape, self-image, perfectionism and negative self-evaluation leads to unregulated dieting, weight loss and malnutrition.

These patients require medical, nutritional and psychiatric support. Anorexia nervosa patients are known to grow fine, downy lanugo on the sides of the face, arms, and back. The condition differentiated from hirsutism, as in hirsutism only terminal hair is involved. Completely treating the anorexia nervosa can resolve the skin condition.

Lanugo in malignancy

Acquired lanugo-type hypertrichosis or hypertrichosis lanuginosa acquisita is sometimes associated with malignancy. Some patients affected by cancers have been observed to have such manifestations, though they may be lanugo-free as babies. The study by Slee PH et al concluded that malignancy associated lanugo is predominant in female patients in the age group of forty years to seventy years. It is observed in patients with colorectal cancer, lung cancer and breast cancer. They stressed that "the appearance of lanugo-type hypertrichosis in body areas previously perceived by patients as 'hairless' is highly indicative of internal malignancy."

Congenital lanugo in babies?

Hypertrichosis lanuginosa congenita, congenital lanugo-type hypertrichosis, is a rare skin disorder seen in some newborn babies. Vibhu Mendiratta et al in their case study on "Hypertrichosis lanuginosa congenita" reported about a three months old male baby. Babies born with this autosomal dominant cutaneous disorder, present lanugo hair covering the entire body. The palms, soles of the feet and mucous membranes are spared.

In these babies the hypertrichosis condition may increase or decrease with age. Lanugo babies may continue to have this type of hypertrichosis even after puberty. Hypertrichosis lanuginosa congenita may be associated with several other congenital defects in babies. In this particular case the baby was without any other manifestations of congenital defects.
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Reference:
1.Jeffrey M Brown, Philip S Mehler, R Hill Harris. Medical complications occurring in adolescents with anorexia nervosa. West J Med. Mar 2000; 172(3): 189–193.
2.Mendiratta V1, Harjai B, Gupta T. Hypertrichosis lanuginosa congenita. Pediatr Dermatol. 2008 Jul-Aug;25(4):483-4.
3.Slee PH, van der Waal R, Schagen van Leeuwen JH, Tupker RA, Timmer R, Seldenrijk CA, van Steensel MA. Paraneoplastic hypertrichosis lanuginosa acquisita: uncommon or overlooked? Br J Dermatol. 2007 Dec;157(6):1087-92. Epub 2007 Oct 17.
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Image source: https://embryology.med.unsw.edu.au/embryology/index.php/File:Hair_development_stages.jpg | Dr Mark Hill | Creative Commons Attribution License
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