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Exogenous ochronosis
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Exogenous ochronosis

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Contributors: Chris G. Adigun MD, Belinda Tan MD, PhD, Lowell A. Goldsmith MD, MPH
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Synopsis

Ochronosis is a condition in which polymerized homogentisic acid is deposited within skin and other structures that contain collagen. The polymer appears clinically as a blue-black pigment. The inherited condition, alkaptonuria, is a systemic disease caused by the lack of both renal and hepatic homogentisic oxidase. This leads to excretion of homogentisic acid in the urine, which gives it a black-stained color. Brown-black pigment, known as ochronotic pigment, is also deposited in connective tissue and leads to ochronotic arthropathy.

Exogenous ochronosis, also known as pseudo-ochronosis, occurs when an external substance is applied to the skin, causing the accumulation of homogentisic acid and subsequent deposition of brown-black pigment in the dermis. This leads to the development of blue, brown, or blackish mottled macules in the areas of application. Phenolic intermediates, such as hydroquinone, carbolic acid (phenol), picric acid, quinine injection, and resorcinol all have the potential to cause exogenous ochronosis. All of these substances are used as skin bleaching agents, typically by people with skin phototypes IV-VI, in cosmetic formulations in an attempt to lighten normally dark skin. Hydroquinone specifically has the capability to inhibit the enzyme homogentisic oxidase in the skin. This leads to accumulation of homogentisic acid locally, which consequently polymerizes to form ochronotic pigment. Hydroquinone is the most common etiologic agent of exogenous ochronosis.

Systemic ochronosis and exogenous ochronosis are identical histologically. Both conditions have the characteristic ochre bodies: yellow-brown, banana-shaped fibers within the papillary dermis.

Initially, it was thought that only high concentrations of hydroquinone had the potential to cause exogenous ochronosis. As a result, many countries set an upper limit of 2% in cosmetic products. However, more recent reports indicate that concentrations as low as 2% may also cause ochronosis. It may not be the higher concentration of the hydroquinones but rather the extended use of the substances that leads to the development of exogenous ochronosis.

Codes

ICD10CM:
E70.8 – Other disorders of aromatic amino-acid metabolism

SNOMEDCT:
410041002 – Exogenous ochronosis

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Differential Diagnosis & Pitfalls

Best Tests

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Therapy

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Drug Reaction Data

Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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References

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Last Updated: 01/30/2018
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Exogenous ochronosis
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Exogenous ochronosis : Face, Hyperpigmented patch, Neck, Cheeks
Clinical image of Exogenous ochronosis
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