It is an inherited disorder characterized by brittle hair, which can 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, reduced fertility , and short stature.
Without photosensitivity, the condition has been termed IBIDS, and without ichthyosis, BIDS. Many patients have recurrent infections, and bone and tooth abnormalities can also occur.
The defining feature of trichothiodystrophy is brittle hair, which is sulfur deficient and, when examined under a microscope and polarized light, shows a characteristic band of light and dark (tiger’s tail).
Trichothiodystrophy and pregnancy
Signs that a woman may be pregnant with a child with TTD include:
- Preeclampsia, high blood pressure, and excess protein in the urine after 20 weeks of pregnancy.
- HELLP syndrome, a life-threatening liver disorder believed to be a type of severe pre-eclampsia.
- Premature birth.
Signs and symptoms
Trichothiodystrophy is characterized by brittle hair and low sulfur content. The skin in many areas of the body may be covered with fine, dark scales (ichthyosis).
Evidence of ichthyosis may be present at birth in the form of a parchment-like membrane (collodion).
Patients are generally short in stature and may have developmental delay and recurrent infections.
Patients’ skin can easily burn after minimal exposure to ultraviolet radiation, and their eyes can be affected by intense light.
Nails can be abnormally short, wide, and rough, and can be easily divided.
Subcutaneous fat loss can result in a prematurely old face and there may be a peaked nose, a receding chin, and protruding ears.
The central nervous system can be affected by seizures, tremors, lack of muscle coordination, and nerve deafness.
The testes may not descend (cryptorchidism) in males and the female genitalia may be underdeveloped.
In women, breast tissue may be completely absent despite normal nipple development. Very small cataracts can occur in the eyes.
Bone and tooth abnormalities appear in some cases.
Trichothiodystrophy is an inherited disorder transmitted as an autosomal recessive trait. Human traits, including classic genetic diseases, are the product of the interaction of two genes for that condition, one received from the father and the other 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 a normal gene and a gene for the disease, the person will be a carrier of the disease, but generally will not have symptoms.
The risk of transmitting the disease to the children of a couple, both carriers of a recessive disorder, is approximately 25% per pregnancy. Many patients with trichothiodystrophy have abnormalities in genes involved in repairing DNA damage.
Trichothiodystrophy is usually present at birth. Men and women are affected in equal numbers.
Patients who are photosensitive must be protected from exposure to the sun and other sources of ultraviolet radiation.
Developmental delay monitoring may be required with special education services at school.
The skin symptoms of ichthyosis 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 damp.
People with frequent infections can benefit from prophylactic antibiotics. Genetic counseling can be beneficial for families of children with trichothiodystrophy.