History
- Because alkaptonuria is usually autosomal recessive, a family pedigree, in all likelihood, reveals no other affected individuals. However, because many individuals are asymptomatic, the low frequency of affected family members may be due to a lack of ascertainment.
- Despite the intrinsic biochemical defect and the expectation that all affected individuals should excrete urine that becomes black when left standing, a significant number of people with alkaptonuria do not present with this clinical finding.
- The most common history is one of arthritic symptoms confined chiefly to the spine, hips, and knees. Virtually all people with alkaptonuria eventually experience arthritis. Onset of thoracic back pain, lumbar back pain, or both around age 30 years is frequent.
Physical
- Slate blue or gray discoloration may be found in the sclerae or ear cartilage.
- Calcifications may be palpable in the discolored areas, particularly in the cartilage of the ear.
- Joint mobility diminishes, as in osteoarthritis. Ankylosis may be present. Spontaneous fusion of one or more discs may occur, with consequent diminished spinal flexion. Joint effusions, particularly in the knee are common and range of motion may be significantly diminished.
- Signs of aortic or mitral valvulitis may be present.
Causes
- Inability to convert homogentisic acid to maleylacetoacetic acid results in accumulation of the former. Homogentisic acid is subsequently converted to benzoquinone acetic acid and spontaneously polymerized. Deposition of the polymer in association with cartilage is the initiating pathophysiologic cause of the arthritis.
- Although unproven, the deposition of polymer is assumed to also cause an inflammatory response that results in calcium deposition in affected joints.
- Exogenous agents including quinacrine (Atabrine), carbolic acid, and hydroquinone have been reported to cause an ochronotic picture without the joint disease. All have been reversible.
Garrod AE. The incidence of alkaptonuria: a study in chemical individuality. 1902 [classical article]. Yale J Biol Med. Jul-Aug 2002;75(4):221-31. [Medline].
Oexie K, Engel K, Tinschert S, et al. Three-generational alkaptonuria in a non-consanguineous family. J Inherit Metab Dis. Dec/2008;Epub:Epub.
US Preventive Services Task Force. Screening for phenylketonuria (PKU): US Preventive Services Task Force Reaffirmation recommendation. Ann Fam Med. Mar-Apr 2008;6(2):166. [Medline].
Peker E, Yonden Z, Sogut S. From darkening urine to early diagnosis of alkaptonuria. Indian J Dermatol Venereol Leprol. Nov-Dec 2008;74(6):700. [Medline].
de Haas V, Carbasius Weber EC, de Klerk JB, et al. The success of dietary protein restriction in alkaptonuria patients is age-dependent. J Inherit Metab Dis. Dec 1998;21(8):791-8. [Medline].
Ffolkes LV, Brull D, Krywawych S, Hayward M, Hughes SE. Aortic stenosis in cardiovascular ochronosis. J Clin Pathol. Jan 2007;60(1):92-3. [Medline].
Fisher AA, Davis MW. Alkaptonuric ochronosis with aortic valve and joint replacements and femoral fracture: a case report and literature review. Clin Med Res. Nov 2004;2(4):209-15. [Medline].
Keller JM, Macaulay W, Nercessian OA, Jaffe IA. New developments in ochronosis: review of the literature. Rheumatol Int. Mar 2005;25(2):81-5. [Medline].
Levine HD, Parisi AF, Holdsworth DE, Cohn LH. Aortic valve replacement for ochronosis of the aortic valve. Chest. Oct 1978;74(4):466-7. [Medline].
Lorenzini S, Mannoni A, Selvi E. Alkaptonuria. N Engl J Med. Apr 3 2003;348(14):1408; author reply 1408. [Medline].
Mayatepek E, Kallas K, Anninos A, Muller E. Effects of ascorbic acid and low-protein diet in alkaptonuria. Eur J Pediatr. Oct 1998;157(10):867-8. [Medline].
O'Brien W, La Du BN, Bunim JJ. Biochemical, pathological and clinical aspects of alcaptonuria, ochronosis and ochronotic arthropathy: review of the world literature (1584-1962). Am J Med. 1963;34:813-38.
Perry MB, Suwannarat P, Furst GP, Gahl WA, Gerber LH. Musculoskeletal findings and disability in alkaptonuria. J Rheumatol. Nov 2006;33(11):2280-5. [Medline].
Phornphutkul C, Introne WJ, Perry MB, et al. Natural history of alkaptonuria. N Engl J Med. Dec 26 2002;347(26):2111-21. [Medline].
Suwannarat P, O'Brien K, Perry MB, et al. Use of nitisinone in patients with alkaptonuria. Metabolism. Jun 2005;54(6):719-28. [Medline].
Vavuranakis M, Triantafillidi H, Stefanadis C, Toutouzas P. Aortic stenosis and coronary artery disease caused by alkaptonuria, a rare genetic metabolic syndrome. Cardiology. 1998;90(4):302-4. [Medline].
Watts RW, Watts RA. Alkaptonuria: a 60-yr follow-up. Rheumatology (Oxford). Feb 2007;46(2):358-9. [Medline].
Wolff JA, Barshop B, Nyhan WL, et al. Effects of ascorbic acid in alkaptonuria: alterations in benzoquinone acetic acid and an ontogenic effect in infancy. Pediatr Res. Aug 1989;26(2):140-4. [Medline].

