From metabolic disorders, osteoporosis is found in ochronotic arthropathy of the spine and large joints of the extremities. It is assumed that it is the secondary form of osteoporosis caused by immobilisation of severely affected individuals. Babel et al. (1960) presented a family affected by alkaptonuria, phenylketonuria and congenital cataract. Alkaptonuria sporadically occurs in coincidence with psoriasis. In 1955, we had the opportunity to present unique coincidence of alkaptonuric ochronosis and ankylosing spondylitis in a 51-year-old male patient (Urbánek and Siťaj 1955). Our patient came from the family in which 4 out of 5 siblings had ochronotic arthropathy. On the basis of analysis of clinical and X-ray findings in the area of spine, it could be anticipated that ochronotic arthropathy and AS mutually interact. Our patient had typical ochronotic changes, especially the calcifications of intervertebral discs less pronounced than other patients in the same stage of the disease. Premature rigidity of the spine caused by AS probably prevented development of ochronotic changes expected at his age. On the other hand, in spite of classical AS signs (indistinct sacroiliac joints, ossification of paraspinal ligaments, obliteration of intervertebral joints), the patient experienced inadequately mild pain in the whole course of the disease. The results from our long-term observation of a large group of patients reveal that relatively mild pain is typical for ochronotic arthropathy.

Ochronotic arthropathy is a disease associated with degenerative changes in the spine manifested with severe pain in the spine and large joints such as the shoulder, hip and knee joints.

Lumbar and thoracic spine is most frequently affected. Medical finding: significant stiffness of the spine and reduced spine mobility may resemble symptoms present in ankylosing spondylitis. However, X-ray findings are different and typical for each disease. Acute exacerbation of ochronotic arthropathy may clinically resemble rheumatoid arthritis.

The scientific literature describes the coexistence of ochronosis and rheumatoid arthritis or ochronosis and ankylosing spondylitis in 2.4/1,000 and 0.5/1,000 cases, respectively (Ball 1989).