In Utero Diagnosis of Trichothiodystrophy by Endoscopically-guided Fetal Eyebrow Biopsy

Objective: To describe the prenatal diagnosis of trichothiodystrophy (TTD) through endoscopically-guided fetal eyebrow biopsy.

Materials And Methods: A 32-year-old patient, gravida 4, para 3, with a history of 2 previous infants affected with TTD was referred at 17(5)/(7) weeks for fetal hair biopsy. DNA repair studies had been normal in the previous children. Four 1-mm biopsies were obtained from the external aspect of the fetal eyebrows under direct endoscopic guidance. Fetal hair samples were assessed with polarized microscopy, electron microscopy, hematoxylin and eosin staining, and were also sent for analysis of sulfur content (cystine levels).

Results: The fetal eyebrows were the only adequate source of hair in the early second trimester. The biopsy samples yielded adequate material for all tests. Polarized microscopy showed characteristic banding patterns, but trichoschisis was not apparent. Cystine levels (19 micromol/l) in the biopsy sample were significantly lower than an age-matched (fresh spontaneous abortion) control (368 micromol/l).

Conclusion: Prenatal diagnosis of TTD is possible in the second trimester through endoscopically-guided eyebrow biopsy. An adequate amount of hair is present in the eyebrows by then, and the disease is already manifest. Analysis of sulfur content of the hair samples is preferred over polarized or electron microscopy, as many classic microscopic findings of TTD may not be present in the early second trimester.