E70.29

Other disorders of tyrosine metabolism

A disorder characterized by bluish-black discoloration of the cartilaginous tissues due to accumulation of homogentisic acid. It is associated with alkaptonuria. Signs and symptoms include dark urine, skin pigmentation, and arthritis.

A rare autosomal recessive disorder characterized by abnormalities in the metabolism of phenylalanine and tyrosine. It results in the accumulation in the blood of homogentisic acid which is excreted in the urine. The presence of homogentisic acid in the urine causes its color to turn black. The excessive amount of homogentisic acid in the blood may cause damage to cartilage and heart valves, and may result in the formation of kidney stones.

An inborn error of amino acid metabolism resulting from a defect in the enzyme homogentisate 1,2-dioxygenase, an enzyme involved in the breakdown of phenylalanine and tyrosine. It is characterized by accumulation of homogentisic acid in the urine, ochronosis in various tissues, and arthritis.

The yellowish discoloration of connective tissue due to deposition of homogentisic acid a brown-black pigment). This is due to defects in the metabolism of phenylalanine and tyrosine. Ochronosis occurs in alkaptonuria, but has also been associated with exposure to certain chemicals e.g., phenol, trinitrophenol, benzene derivatives).

What: ochronosis. Ochronosis: the pathologic accumulation of a blue-black pigment in the connective tissues of persons with alkaptonuria, a rare inborn error of metabolism. These persons lack the enzyme homogentisic acid oxidase, resulting in a buildup of homogentisic acid, a precursor of the pigment. Why: the great majority of patients with ochronosis eventually develop an arthropathy clinically resembling degenerative joint disease. How: ochronosis is diagnosed by the combination of pigmentation of the cartilage, the presence of homogentisic acid in the urine, and arthritis usually involving the knees, hips, lumbosacral spine, and shoulders. The slate blue-black pigmentation is most apparent in the sclera of the eyes, the external ears, and the tympanic membranes. The cerumen may also show a dark discoloration. The presence of homogentisic acid in the urine is determined by the dark color which occurs when the urine is alkalinized and by paper chromatography. Refs: schumacher hr and holdsworth de: ochronotic arthropathy i. Clinico-pathologic studies. Semin arthritis rheum 6:207, 1977. Dn19296-1.

E70.29 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.

This is the American ICD-10-CM version of E70.29 – other international versions of ICD-10 E70.29 may differ.