Ochronosis-Calcification of the intervertebral disc

Ochronosis is the bluish black discoloration of certain tissues, such as the ear cartilage and the ocular tissue  seen with alkaptonuria, a metabolic disorder

           Alkaptonuria is a rare autosomal recessive metabolic disorder caused by deficiency of homogentisic acid oxidase, the only enzyme capable of catabolizing homogentisic acid (HGA). Alkaptonuria features a defect in the biochemical pathway by which phenylalanine and tyrosine are normally degraded into fumaric and acetoacetic acid.

 This deficiency results in accumulation and deposition of HGA in cartilage, causing the characteristic diffuse bluish black pigmentation. These affected connective tissue become weak and brittle with time, leading to chronic inflammation, degeneration, and osteoarthritis.

 Alkaptonuria is often recognized at birth when parents note discoloration of the urine

 The fourth decade often marks the onset of thickening and blue-black or gray-blue discoloration of the ear cartilage.

Other body locations that frequently display the alteration in skin hue are the eyelids, the forehead, the cheeks, the axillae, the genital region, the nail beds, the buccal mucosa, the larynx, the tympanic eardrum, and the tendons (most easily demonstrated by the patient making a fist).

Ochronotic arthropathy develops later with arthritic symptoms.

Arthritic signs of ochronotic arthropathy develop in the third and fourth decades. Narrowing of the joint spaces and disk calcifications occur. Lower back, hip, and knee pain and stiffness are not uncommon.

The clinical discoloration of the skin is a result of the formation of ochronotic pigment granules in the dermis and in the apocrine glands. Thus, the ochronotic changes of cartilaginous and tendonous structures are best appreciated in regions in which the overlying skin is of minimal thickness, such as the ears, the nasal tip, and the extensor tendons of the hands.

Differential diagnosis of disc calcification

1.Degenerative spondylosis

2..Alkaptonuria

3.Ankylosing spondylitis

4.Juvenile Chronic Arthritis

5.Haemochromatosis

6.DISH

7.Gout

8.diopathic