It is also known as alkaptonuric ochronosis. It is autosomal recessive metabolic disorder which causes excess production of homogentisic acid resulting in excess of pigmentation, calcification and inflammation of the cartilage and related tissue throughout the body. It is one of inborn errors of metabolism.

 

It occurs due to incomplete metabolism of homogentisic acid, tyrosine and phenylalanine. This disorder involves face, skeletal system, cardiovascular system, respiratory system, urinary system and to less degree the skin. It is a genetic disorder due to deficiency of the enzyme responsible for breakdown of HGA. In this condition the products of phenylalanine and tyrosine accumulates resulting in deposition of homogentisic acid in the connective tissue.

Ochronosis occasionally occur due to exposure of various substances like phenol, trinitrophenol, resorcinol, mercury, picric acid, benzene, hydroquinone and antimalarials.

Signs and symptoms

• Tyndall effect: The pigmented cartilage appear blue due to light scattering phenomenon
• Dark urine
• Pigmentation of skin
• Arthritis
• Deposits around the trachea, larynx and bronchi cal lead to breathlessness and difficulty in breathing
• Deposits around the heart and blood vessel lead to atherosclerotic plaques
• Thickening and blue-black or gray-blue discoloration of the ear cartilage.
• Ochronotic arthropathy
• Gray to brown color in sclera, between the margins of cornea and outer or inner canthus
• Skin discoloration over nasal tip, costochondral junctions, and extensor tendons of hands, cheeks, finger nails and buccal mucosa. Skin color changes are more apparent in areas of sun exposed.

Diagnosis:

• Complete blood count
• X-ray so spine show bamboo spine deformity due to calcification of intervertebral disc spaces.

• X-ray of knee and hip joint shows osteoarthrosis
• Urine turns black after exposure to air for many hours

Diagnosis

There is no specific medical treatment. There is no cure for this condition and the disease is lifelong.

• Symptomatic treatment
• Physical therapy
• Diets low in tyrosine and phenylalanine there by reducing the toxic by product of HGA
• Advised diet rich in vitamin C which prevent oxidation of homogentisic acid