In other species: , crab-eating macaque , rabbit

Possibly relevant human trait(s) and/or gene(s) (MIM number): 203500 (trait)

Mendelian trait/disorder: unknown

Considered a defect: yes

Species-specific description: The three characteristic features of alkaptonuria are homogentisic aciduria, ochronosis, and arthritis (Azami and Maleki, J Res Med Sci. 2015 Oct; 20(10): 1018–1019.) The basic cause is deficiency of the enzyme homogentisate 1,2-dioxygenase (HGD). As explained by Bryan et al. (2016), "When HGD is absent or nonfunctional, a melanin-like pigment derivative of HGA, benzoquinoneacetate, accumulates in tissues and alters collagen cross-linking, causing joint pain and cartilage degeneration".

History: Bryan et al. (2016) were the first to report ochronosis "histologically and ulstrastructurally in a domestic animal species".