Trichothiodystrophy: Photosensitive, TTD-P, TTD, Tay syndrome

Abstract

Abstract Although the term, "trichothiodystrophy" (TTD) refers to the hair anomalies in this group of patients, this is a heterogeneous, multisystem disease in which any or every organ in the body may be affected.1-5 Neuroectodermal derived tissues are particularly likely to be involved. This term was introduced by Price et al in 1980 to designate patients with sulfur-deficient brittle hair, which they recognized as a marker for this complex disease and designated it as a "neuroectodermal symptom complex".6 Patients with TTD have brittle hair and nails (associated with reduced content of cysteine-rich matrix proteins), ichthyotic skin and physical and mental growth retardation.7 Ichthyosis is usually apparent at birth but much less so after the first few weeks of life. Other frequently associated features include ocular cataracts, infections and maternal complications related to pregnancy. Atrophy of subcutaneous fat may also be present. TTD occurs in a pattern of inheritance consistent with an autosomal recessive condition. The disease is extremely heterogeneous in severity and extent, with some patients showing no neurological deficiency.8 Others show severe, multisystem disease. Many patients die at a young age, most commonly due to infectious disease.1 TTD is part of a more broadly defined group of diseases identified as IBIDS (ichthyosis, brittle hair, impaired intelligence, decreased fertility and short stature). Photosensitive cases are also identified as PIBIDS (photosensitivity with IBIDS). Cases without manifest ichthyosis are also identified as PBIDS. These syndromes defy rigorous definition because of clinical variation between patients.5 The original two cases were described by Tay in oriental siblings, whose parents were first cousins; thus the disease is also known as Tay syndrome.9 The hairs in patients with TTD have a distinctive, diagnostically useful appearance on polarized light microscopy consisting of alternating light and dark bands known as the "tiger tail" anomaly. Diagnosis may be confirmed by sulfur content analysis of hair shafts, which shows decreased sulfur and cysteine content.5,7 Approximately half of patients with TTD have photosensitivity, which correlates with a nucleotide excision repair (NER) defect. These patients are designated as having trichothiodystrophy- photosensitive (TTDP). Non-photosensitive patients are designated as having trichothiodystrophy- nonphotosensitive (TTDN). Skin cancer is very rare in sun-sensitive TTD.5,10. © 2010 Landes Bioscience and Springer Science+Business Media.