Trichothiodystrophy is characterized by sparse, short, sulfur-deficient hair. Numerous symptom complexes have been described in which the hair abnormality represents a constant feature. We report a boy with trichothiodystrophy, ichthyotic skin changes, onychodystrophy, chronic neutropenia, osteosclerosis, hypothyroidism, nystagmus, growth and mental retardation, and microcephaly, who developed a progressive encephalopathy with ataxia and optic atrophy at 2.5 years of age. In addition to a deficient cystine level identified on a hair sample, a disturbance in the composition of other amino acids was present. Although features were reminiscent of osteosclerosis, ichthyosis, brittle hair due to trichothiodystrophy, impaired intelligence, decreased fertility, and short stature (SIBIDS) and could represent a variant of this disorder, findings in our patient may reflect a new trichothiodystrophy symptom complex that carries a poor prognosis for survival beyond childhood.