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NORD is very grateful to the members of the Medical and Scientific Advisory Board of the Foundation for Ichthyosis & Related Skin Types for assistance in the preparation of this report.
Trichothiodystrophy is a hereditary disorder characterized by brittle hair, which may be accompanied by a variety of other manifestations. It is sometimes called PIBIDS, a term that refers to the association of Photosensitivity Ichthyosis, Brittle hair, Intellectual impairment, Decreased fertility, and Short stature. Without photosensitivity the condition has been termed IBIDS, and without ichthyosis, BIDS. Many patients have recurrent infections, and abnormalities of the bone and teeth may also occur.
The defining feature of trichothiodystrophy is brittle hair, which is sulfur deficient and, when examined with a microscope and polarized light, demonstrates a characteristic light and dark (tiger tail) banding.
Trichothiodystrophy is characterized by brittle hair that is low in sulfur content. The skin in many areas of the body may be covered with fine, dark scales (ichthyosis). Evidence of the ichthyosis may be present at birth in the form of a parchment-like (collodion) membrane. Patients usually have short stature and may have developmental delay and recurrent infections. Patients' skin may burn easily after minimal exposure to ultraviolet radiation (e.g., sun) and their eyes may be bothered by strong light (photophobia). Nails may be abnormally short, broad and ridged, and they may split easily. Loss of subcutaneous fat may result in a prematurely old-looking face and there may be a beaked nose, receding chin, and protruding ears.
The central nervous system may be affected with seizures, tremors, lack of muscle coordination, and nerve deafness. The testes may fail to descend (cryptorchidism) in males and female genitalia may be underdeveloped. In women, breast tissue may be completely absent in spite of normal development of the nipples. Very small cataracts may occur in the eyes. Bone and teeth abnormalities appear in some cases
Trichothiodystrophy is a hereditary disorder transmitted as an autosomal recessive trait. Human traits, including the classic genetic diseases, are the product of the interaction of two genes for that condition, one received from the father and one from the mother. In recessive disorders, the condition does not appear unless a person inherits the same defective gene for the same trait from each parent. If the individual receives one normal gene and one gene for the disease, the person will be a carrier for the disease but usually will not show symptoms. The risk of transmitting the disease to the children of a couple, both of whom are carriers for a recessive disorder, is approximately 25 percent per pregnancy. Many patients with trichothiodystrophy have abnormalities in genes involved in the repair of DNA damage.
Trichothiodystrophy is usually present at birth. Males and females are affected in equal numbers.
Symptoms of the following disorders may resemble those of trichothiodystrophy. Comparisons may be useful for a differential diagnosis.
"Ichthyoses" or "disorders of cornification" are general terms describing a group of scaly skin disorders. They are characterized by an abnormal accumulation of large amounts of dead skin cells (squames) in the top layer of skin. The conversion of an abnormally large number of epidermal cells into squamous cells is thought to be caused by a defect in the metabolism of skin cells known as "corneocytes" or of the fat-rich matrix around these cells. The cells can be thought of as bricks, while the matrix would be the mortar holding these cells together.
Xeroderma pigmentosum is a disorder in which damage done by ultraviolet light (especially sun light) is not repaired properly leading to dry skin with heavy freckling and development of skin cancer at a young age. Patients may also have progressive neurologic impairment. Xeroderma pigmentosum is also due to mutations in genes involved in DNA repair.
Patients who are photosensitive must be protected from exposure to the sun and other sources of ultraviolet radiation. Monitoring for developmental delay with special educations services may be required in school. Skin symptoms of ichthyosis (dry skin) are treated by applying skin softening emollients and keratolytics (products containing alpha-hydroxy acids). This can be particularly effective after bathing while the skin is still moist. Individuals with frequent infections may benefit for prophylactic antibiotics. Genetic counseling may be beneficial for families of children with trichothiodystrophy.
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Sybert, VP. Ichthyosis. In: NORD Guide to Rare Disorders. Lippincott, Williams & Wilkins. Philadalphia, PA. 2003:120-21.
DiGiovanna JJ: Ichthyosiform Dermatoses. In Freedberg IM, et al (Eds), Fitzpatrick's Dermatology in General Medicine, 6th Edition. McGraw-Hill, New York, 2003;51:481-505.
DiGiovanna, JJ, Robinson-Bostom, L. Ichthyosis: etiology, diagnosis, and management. Am J Clin Dermatol. 2003;4: 81-95.
Williams, ML, et al. Genetically Transmitted, Generalized Disorders of Cornification. The Ichthyoses. Dermatol Clin. January 1987; 5(1): 155-78.
Happle, R, et al. The Tay Sydrome (Congenital Ichthyosis with Trichothiodystrophy). European Journal Pediatr. January 1984;141(3): 147 /152.
Report last updated: 2008/04/01 00:00:00 GMT+0