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Abstract

Background  Endogenous ochronosis (EO) is a rare autosomal recessive disorder due to accumulation of oxidized and polymerized forms of homogentisic acid (HGA) in connective tissues, giving them a deep dark blue pigmentation.

Aim  Through a new Tunisian case of EO and a review of the literature, we aimed to define the epidemioclinical features of EO, its diagnostic criteria, and evolution.

Methods  Three hundred and forty patients were enrolled through 54 articles and four abstracts.

Case report  A 35-year-old woman, born in consanguineous parents, presented with blue-grey patches of fingernails, first interdigital spaces, and ears with brown conjunctival pigmentation. Urine specimen turned dark on standing overnight. The diagnosis of EO was confirmed by urinary high levels of HGA. Investigations revealed radiologic signs of ochronotic arthropathy.

Review of the literature  EO is ubiquitary. Its prevalence was estimated at almost 6.5 cases/year. The mean age at diagnosis was 55.9 years (M/F: 1.85). Onset symptoms mainly consisted in cutaneous signs. Ochronotic arthropathy was the most frequently reported manifestation. Treatment was mainly symptomatic.

Discussion  EO is often revealed in adulthood mainly after the fourth decade. Urinary darkening is the first sign of the disease but is rarely reported as an onset sign. Skin signs are the alerting features. Ochronotic arthropathy is insidious but may be debilitating. No specific medical treatment of EO is available.

Conclusion  Cutaneous manifestations are the hallmarks of OE. As vital organ involvement has been reported, close monitoring and continuous surveillance is warranted.