Skin nontumor
Dermal collagen and elastic tissue alterations, and cutaneous deposits
Ochronosis
Topic Completed: 1 August 2011
Minor changes: 5 August 2020
Copyright: 2002-2020, PathologyOutlines.com, Inc.
PubMed Search: Ochronosis
Table of Contents
Clinical features | Case reports | Microscopic (histologic) description | Additional referencesCite this page: Hamodat M. Ochronosis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/skinnontumorochronosis.html. Accessed October 21st, 2020.
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
- Pigment in dura matter of brain (Arch Pathol Lab Med 2001;125:961), ochronotic arthropathy
Microscopic (histologic) 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 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
