Author(s)

Suma S, Polat P

Patient

female, 33 year(s)

The patient presented with signs of low back pain and restriction in movement.

The patient presented with low backache, gradually increasing over the previous 6 months. There was no history of dark urine or staining of the clothes. Childhood growth and development were normal. Clinical examination showed restriction of movement in the lower back. Most striking was the patient's posture.

Axial computed tomography (CT) of the lumbar spine showed prominent changes in the vertebral bodies and intervertebral disc spaces. CT showed intervertebral disc narrowing, intervertebral disc calcification and multiple vacuum signs in the intervertebral disc spaces(Fig. 1).

Sagittal magnetic resonance imaging (MRI) sections showed flattening of lumbar lordosis. Intervertebral disc spaces were narrow. There was a prominent signal loss at the intervertebral disc spaces on both T1- and T2-weighted MR images.On T1-weighted spin-echo sagital images, the disk TH12/L1 exhibited bright signal intensity, probably due to ossification and calcification of the disk.

Alkaptonuria is a rare hereditary autosomal recessive metabolic disease characterised by a triad of homogentesic aciduria, arthritis and ochronosis (1,2). Ochronosis is the musculoskeletal manifestation of alkaptonuria. It affects especially large joints (hip, knees and vertebral column) with a progressive degenerative arthrosis. The extra-articular manifestations are ocular and skin pigmentation, genitourinary calculi and cardiovascular ochronosis (especially of the aortic valve). The symptoms mostly begin in the third or fourth decades of life.

Ochronotic pigments increase the degeneration of cartilage. This leads to a brittleness and fragmentation of the cartilage causing a non-specific synovitis and ochronotic arthritis which simulates osteoarthritis radiologically. Also typical is the ochronotic spondylosis in the lumbar spine. The stiffness of the back slowly progresses to a complete rigidity with flattening of the lumbar lordosis and dorsal hyperkyphosis resembling ankylosing spondylitis. Changes suggesting alkaptonuria are degeneration and narrowing of the intervertebral disc with calcification of the remaining disc material. In contrast to ankylosing spondylitis, syndesmophytes or annular ossification with a bamboo pattern do not occur. The lumbar spine is affected first, followed by the thoracic and cervical spine (3).

Computed tomography can reveal prominent changes in intervertebral disc material. Calcification is seen as increased density. The vacuum phenomenon is seen as hypodense areas representing air in the degenerative disc material. Intervertebral discs show prominent signal loss due to calcification and the vacuum phenomenon on both T1- and T2-weighted MRI sections. But in our case bright signal intensity at TH12/L1 disk on T1-weighted images was attributed to calcification or ossification of the disk. Because corresponding CT sections showed marked calcifications in that disk. The bright signal intensities consistent with calcification can be attributed the content of calcification on T1-weighted MR image. Spinal canal narrowing and prolapses can also be detected successfully by MRI.