Abstract
BackgroundOchronosis/Alkaptonuria is a tyrosine metabolism disorder where accumulation of homogentisic acid, in eye, skin, cartilage and several other connective tissues leads to a black pigmentation of the affected tissues. It is autosomal-recessive inherited in men with a frequency of 1-9/1,000,000. While it is clear that pigment deposits lead to joint destruction, renal stone formation and cardiac valvulopathy respectively, the significance of ocular findings is still unclear. We therefore aim to evaluate the frequency and clinical significance of ocular findings in ochronosis and discuss possible therapeutic options.MethodsSystematic review of literature via Medline and Web of Science. Only case reports in English, German, French, Spanish or Italian documenting detailed ophthalmologic examination were included.ResultsOur search revealed 36 case reports including 40 patients. Average age at the onset of ocular signs was 40.6 years. The most frequent sign was symmetric brown sclera pigmentation present in 82.5 percent of the patients. “Oil-drops”, brown pigment spots in the limbus are generally considered pathognomonic but were a little less frequent (75 percent). Vermiform pigment deposits at the level of the conjunctiva or increased conjunctival vessel diameter is also frequent. We found an increased incidence of central vein occlusion and elevated intraocular pressure going along with chamber angle hyperpigmentation. Another condition observed twice is rapid progressive astigmatism attributable to corneoscleral pigment accumulation.ConclusionOur observations suggest that ocular findings are of double relevance. First, characteristic ocular findings can anticipate the time of diagnosis and second, ocular findings may complicate to various conditions putting sight at risk. Opthalmologists and general physicians should be aware of both. Therapeutic options include protein restriction, administration of high dose vitamin C or nitisonone. Evidence for all of them is limited.
Highlights
Ochronosis/Alkaptonuria is a tyrosine metabolism disorder where accumulation of homogentisic acid, in eye, skin, cartilage and several other connective tissues leads to a black pigmentation of the affected tissues
The age at which the ocular findings first appeared was only given in eight articles [25,26,27,28,29,30,31,32] and was 40.6 (Standard deviation: ±9.8, range 25 to 54) years
In conclusion, ocular findings are frequent in patients suffering from ochronosis
Summary
Ochronosis/Alkaptonuria is a tyrosine metabolism disorder where accumulation of homogentisic acid, in eye, skin, cartilage and several other connective tissues leads to a black pigmentation of the affected tissues. It is autosomal-recessive inherited in men with a frequency of 1-9/1,000,000. Alkaptonuria (AKU/hereditary ochronosis/homogentisic acid oxidase deficiency/ORPHA56) is a rare autosomal recessive condition where tyrosine metabolism is disturbed [1,2]. In AKU, homogentisic acid 1,2 dioxygenase (HGO, EC 1.13.11.5) is mutated [1]. While the genetic defect, resulting in brown discoloration of urine is referred to as alkaptonuria, the term hereditary ochronosis is applied for the tissue manifestation of the disease, classically including cartilage, skin and sclera [10,13]. Cartilage involvement is probably the most striking feature, accurately described by Rudolf Virchow who developed the term “ochronosis” [14]
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