Radiographic and MRI findings in ochronosis

Purpose. Ochronotic arthropathy is the articular manifestation of alkaptonuria, a rare hereditary metabolic disease that leads to the deposition of homogentisic acid particularly in the joints where it causes articular degeneration and inflammation. We studied the radiological patterns of the disorder using both traditional X-rays both MRI and comparing the results obtained with the two techniques. Materials and methods. The study included five patients (4 males, 1 female, mean age 51 years); we studied the most frequently affected sites, the knee, the shoulder and the spine. As regards the conventional study we used a radiographic score which considered the state of the articular space and the presence of calcifications. MRI of the peripheral joints was performed on the most symptomatic site or, if asymptomatic, on the most severely affected site as established by radiography; in all cases T1 - and T2- weighted sequences in the axial, sagittal and coronal planes were acquired. Results. Both the X-ray and MRI study revealed the typical alterations of ochronosis in the cases with a known diagnosis: articular space narrowing up to osseous ankylosis, calcifications, osteophytosis, reactive sclerosis of the articular surfaces; MRI was however more accurate in identifying the alterations and revealing lesions not visible at conventional radiology, such as ligament lesions. In the case of newly diagnosed ochronotic arthropathy MRI proved valuable for its ability to detect alterations that are poorly appreciable at conventional radiology. Conclusions. Modern diagnostic imaging, above all MRI, allowed us to identify the peculiar characteristic features of ochronosis and is fundamental both for the diagnosis and for differentiating ochronosis from other articular disorders.