Abstract: Trichothiodystrophy is characterized by sparse, short, sulfur-deflclent hair. Numerous symptom complexes have been described in which the hair abnormaiity represents a constant feature. We report a boy with trichothiodystrophy, ichthyotic skin changes, onychodystrophy, chronic neutropenia, osteoscierosis, hypothyroidism, nystagmus, growth and mentai retardation, and microcephaiy, who developed a progressive encephalopathy with ataxia and optic atrophy at 2.5 years of age. in addition to a deficient cystine ievei identified on a hair sampie, a disturbance in the composition of other amino acids was present. Ai-though features were reminiscent of osteoscierosis, ichthyosis, brittie hair due to trichothiodystrophy, impaired inteliigence, decreased fertiiity, and short stature (SIBIDS) and couid represent a variant of this disorder, findings in our patient may refiect a new trichothiodystrophy symptom compiex that carries a poor prognosis for survivai beyond chiidhood.