Despite many speculations that this polymer deposition is associated with cardiac pathology, no reports of mortality directly related to the homozygous state for alkaptonuria exist. There are reports of calcification and stenosis of the aortic annulus leading to coronary artery disease, and the incidence of myocardial infarction in higher than normal in older patients with ochronosis. The true frequency of alkaptonuria cannot be given with certainty for a number of reasons. To further complicate this picture, reports in the literature indicate wide variability in incidence, particularly where gene pools are highly restricted. In certain areas, an incidence as high as 1 in every 25,000 live births has been reported.
Life expectancy is normal.
Males tend to have an earlier onset of arthritic symptoms with a greater degree of severity than females, although the reason for this difference is unclear. Clinical symptoms, aside from dark-stained diapers, generally are present only after the third decade. Since alkaptonuria is autosomal recessive, a family pedigree will, in all likelihood, show no other affected individuals. However, since many individuals are asymptomatic, it could be argued that the low frequency of affected family members may be due to lack of ascertainment. Despite the intrinsic biochemical defect and the expectation that all affected individuals should excrete urine that becomes black upon standing, a significant number of patients do not present with this clinical finding.