title: Ochronosis-like condition in a cat.
abstract: BACKGROUND
  Endogenous ochronosis is caused by a defect in the enzyme homogentisate 1,2-dioxygenase (HGD), which results in abnormal pigment deposition in the skin and urine abnormalities. Ochronosis previously has not been described histologically or ultrastructurally in a domestic animal species.
  
  
  OBJECTIVE
  To describe the clinical, histopathological and ultrastructural findings in a case of aberrant pigmentation in a cat with features that resemble ochronosis.
  
  
  METHODS
  A 5-year-old, spayed female Domestic short hair cat presented with multiple black cutaneous plaques on the face and progressive lethargy. The cat's urine turned brown when exposed to air. The familial history of the cat was unknown.
  
  
  METHODS
  Clinical examination; histopathology, electron microscopy and mass/energy dispersive X-ray spectroscopy of tissues.
  
  
  RESULTS
  Septic peritonitis and additional pigment in the spleen, intestine and lymph node were found at postmortem examination. The pigment was determined to be an organic compound and had a similar histological appearance, staining properties, ultrastructure and composition to ochronotic pigment. No mutations were found in exons 3, 6, 8 and 13 of the HGD gene in the cat.
  
  
  CONCLUSIONS
  To the best of the authors' knowledge, this is the first report of a condition resembling ochronosis in a domestic animal species that has been evaluated with histopathology and advanced imaging techniques. It provides an additional differential in cases of aberrant pigmentation in cats.
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, 4467 TAMU, College Station, TX, 77843-4467, USA.
authors.forename: Laura K
authors.identifier: http://orcid.org/0000-0003-0746-9461
authors.initials: LK
authors.lastname: Bryan
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, 4467 TAMU, College Station, TX, 77843-4467, USA.
authors.forename: Brad R
authors.initials: BR
authors.lastname: Weeks
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, 4467 TAMU, College Station, TX, 77843-4467, USA.
authors.forename: Harold Ross
authors.initials: HR
authors.lastname: Payne
authors.affiliation: Animal Dermatology Clinic, 3901 East 82nd Street, Indianapolis, IN, 46240, USA.
authors.forename: Lori A
authors.initials: LA
authors.lastname: Thompson
authors.affiliation: Department of Veterinary Pathobiology, College of Veterinary Medicine and Biomedical Sciences, Texas A&M University, 4467 TAMU, College Station, TX, 77843-4467, USA.
authors.forename: Joanne L
authors.initials: JL
authors.lastname: Mansell