Trichothiodystrophy: role of a dermato-trchologist.

Sir,

We report here a 3.5-year-old boy was referred to dermatology clinic from a pediatric neurologist for consultation about skin problems. He was the second child of the family. Parents were cousins. He suffered from skin problems as well as some developmental delays from his birth. He had short stature and could only speak about 20 words. Physical examination revealed severe dry skin with prominent fine white scaling without any erythema as ichthyosiform dermatitis over much of the body that was most prominent on the extensor surface of the upper and lower extremities, palmoplantar dryness and hyper linearity and short, unruly, irregular sparse hair on the scalp and eyebrows [Figure 1a and b]. There was no nail or mucosal abnormality and no history of photosensitivity. His physical examination in otherwise was insignificant. Samples were taken from his scalp and eyebrows for assessing microscopic evaluation that revealed trichoschisis and trichorrhexis nodosa and characteristics intermittent bright and dark bands under the polarized microscopy [Figure 2a and b]. Measurement of sulfur content in hair samples showed a sulfur deficiency (2.4%) which was <50% of normal value (normal content varied between 4.6% and 5.4%).[1] Based on our clinical and other findings Trichothiodystrophy, ichthyosis, brittle sulfur- deficient hairs, developmental delay, intellectual impairment and short stature (IBIDS) type was diagnosed.

Figure 1

(a) Short, irregular spare hair on the scalp, (b) ichthyosiform dermatitis on left leg

Figure 2

(a) Trichoschisis (transverse fractures), (b) intermittent bright and dark bands under polarized microscopy

TTD is an autosomal recessive disorder that is characterized by sulfur deficient, brittle hair and a wide spectrum of clinical manifestations including photosensitivity, ichthyosis, intellectual impairment, short stature, microcephaly, characteristic facial features (protruding ears, micrognathia) and decreased fertility.[1]

The disorder is caused by a sulfur deficiency in tissues of neuroectodermal origin.[2] And can be classified according to the constellation of features accompanied by the hair changes.[3]

A review of 112 patients noted a wide spectrum of clinical features that varied from patients with only hair involvement to those with profound developmental defects. Common features included intellectual impairment (86%), short stature (73%), ichthyosis (65%), ocular abnormalities (51%), infections (46%) and photosensitivity (42%). More than half of the patients had abnormal characteristics at birth and 19 patients died before the age of 10.[4]

The hair, with sulfur reduced to 50% of the normal value, has distinctive features under polarizing, light and scanning electron microscopy. With polarizing microscopy, the hair shows alternating bright and dark regions that give a striking striped, or tiger tail appearance but the pattern may not be evident at birth.[5]

By light microscopy, hair shafts demonstrate transverse fractures (trichoschisis) in conjunction with an irregular surface and diameter. Occasionally, trichorrhexis nodosa or 180° twists as in pilitorti may be observed. Polarizing light microscopy is the gold standard for detecting the characteristic light and dark bands, the so-called “tiger tail” or “zigzag” pattern.

We report this case to emphasis on the importance of careful hair examination for diagnosis of such rare diseases preferably by a dermato-trichologist because hair shaft abnormalities are extremely common in genodermatoses and hair changes may be a significant finding or even the initial presentation of a syndrome giving the clue to the diagnosis, that often lack macroscopic features, which would enable easy diagnosis in medical practice.