Skin-nontumor / Clinical dermatology
Other dermatoses
Ochronosis

Author: Mowafak Hamodat, M.D., MB.CH.B, MSc., FRCPC (see Authors page)

Revised: 18 July 2016, last major update August 2011

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PubMed Search: Ochronosis

Cite this page: Ochronosis. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/skinnontumorochronosis.html. Accessed December 5th, 2016.
Clinical Features
  • Autosomal recessive disorder of increased urinary excretion of homogentisic acid (alkaptonuria), with deposition of “ochre-colored” pigment in collagen-rich regions (ochre: moderate orange-yellow)
  • Occurs in 50% with alkaptonuria
  • Due to disorder of homogentisic acid oxidase gene on #3q, intermediate component in metabolism of tyrosine and phenylalanine, causing accumulation of benzoquinone acetic acid, which binds to collagen irreversibly
  • Clinically black pigmentation of joints (arthritis with pigment deposition in cartilage and intervertebral disks), cardiovascular system (valvular calcifications and stenosis), kidney (black urine, pigmented stones) and skin (cutaneous pigmentation)
  • Also involvement of sclera of eye
Case Reports
Micro Description
  • Yellow–brown sharply defined irregularly shaped and frequently fragmented fibers in superficial dermis
  • Ochronotic pigment is autofluorescent, appears black with methylene blue, but does not stain with Van Gieson or Pearl’s stain or the Masson Fontana reaction
  • Pigment granules often present in epithelium and basement membrane of sweat glands, in endothelium and within dermal macrophages
  • Hydroquinone induced ochronosis shows melanophages in upper dermis associated with depigmentaion of the epidermal melanocytes
  • In early lesions, collagen fibers appear basophilic and swollen before developing characterstic yellow ochronotic morphology
  • With chronicity, large amorphous eosinophilic granules may develop resembling colloid milium
  • Solar elastosis and foregn body granuloma are common features
  • Pigmentation secondary to antimalarial drugs is due to melanin and hemosiderin deposition in addition to the classic ochronotic fibers
Additional References