Alkaptonuria (ochronosis) is an autossomal recessive disorder which results from an innate error of phenylalanine and tyrosine's metabolism. This defect causes accumulation of homogentisic acid on the tissue and usually is excreted in the urine. This disorder results from a complete deficiency of the homogentisate 1,2 - dioxygenasc (HGO) caused by chromosome 3q(3q21-q23) mutation. The clinical features include: ochronotic artropathy, black-gray pigmentation of the cartilage and the mine turns black. This is a rare disorder and incidence is about 1-4 in 1.000.000 of people and the prevalence is higher in consanguineous groups. The author will desczibe two affected brothers and discuss the pathophysiology, clinical features, diagnosis and treatment of ochronosis.
Brandão, L. R., Borjaille, B. P., Hasegawa, T. M., Rosa, R. F., Azevedo, E., & Chahade, W. H. (2006). Alkaptonuria (ochronosis): Report of two cases. Revista Brasileira de Reumatologia, 46(5), 369–372. https://doi.org/10.1590/s0482-50042006000500014