title: Confocal microscopy of corneal crystals in a patient with hereditary tyrosinemia type I, treated with NTBC.
abstract: OBJECTIVE
  To describe the confocal microscopic findings in a patient with hereditary tyrosinemia type I (HT-I) treated with 2-(2-nitro-4-trifluoromethylbenzoyl)-1,3-cyclohexanedione (NTBC) who developed corneal crystals.
  
  
  METHODS
  In this case study, we describe the confocal microscopic findings in a boy, who was diagnosed with HT-I at the age of 4 months. At 16 years of age, he developed painful corneal lesions in both eyes. On slit-lamp examination, whorl-like branching epithelial corneal lesions were found, staining faintly with fluorescein. His NTBC treatment was stopped and reintroduced at a lower dose after 1 month. The lesions clearly regressed, leaving only mild residual epithelial scarring, without fluorescein staining and without pain. Confocal microscopy was performed in the acute painful stage and in the asymptomatic convalescent stage 5 months later.
  
  
  RESULTS
  Confocal microscopy confirmed the presence of slender birefringent spiky crystals in the very superficial corneal epithelium. In the asymptomatic convalescent phase, the crystals clearly persisted on confocal microscopy, although they were barely visible on slit-lamp examination.
  
  
  CONCLUSIONS
  This is the first in vivo demonstration by confocal microscopy of corneal crystals present in a patient with proven type I tyrosinemia, under NTBC treatment.
authors.affiliation: Department of Ophthalmology, Ghent University Hospital, Ghent, Belgium. ppschauwvlieghe@hotmail.com
authors.forename: Pieter-Paul
authors.initials: PP
authors.lastname: Schauwvlieghe
authors.forename: Jaak
authors.initials: J
authors.lastname: Jaeken
authors.forename: Philippe
authors.initials: P
authors.lastname: Kestelyn
authors.forename: Ilse
authors.initials: I
authors.lastname: Claerhout
mesh_terms: D015111:4-Hydroxyphenylpyruvate Dioxygenase / Q000037:antagonists & inhibitors; D000293:Adolescent; D003318:Corneal Opacity / Q000175:diagnosis* / Q000188:drug therapy / Q000201:enzymology; D003460:Crystallization; D003512:Cyclohexanones / Q000627:therapeutic use*; D004791:Enzyme Inhibitors / Q000627:therapeutic use*; D019573:Epithelium, Corneal / Q000187:drug effects / Q000201:enzymology / Q000473:pathology*; D019793:Fluorescein / Q000378:metabolism; D006801:Humans; D008297:Male; D018613:Microscopy, Confocal; D009579:Nitrobenzoates / Q000627:therapeutic use*; D013194:Staining and Labeling; D020176:Tyrosinemias / Q000175:diagnosis* / Q000188:drug therapy / Q000201:enzymology
chemical_list: D003512:Cyclohexanones; D004791:Enzyme Inhibitors; D009579:Nitrobenzoates; D015111:4-Hydroxyphenylpyruvate Dioxygenase; C077073:nitisinone; D019793:Fluorescein