Ochronosis as a cause of secondary osteoarthrosis
Bashkova I.B.^1,2, Kichigin V.A.¹, Shaipov R.Sh.², Kryuchkov N.A.², Bezlyudnaya N.V.², Didichenko S.N.², Borisova L.V.<sup>2

1</sup> Chuvash State University named after I.N. Ulyanov, Cheboksary, 
² The Federal center of traumatology, orthopedics and endoprosthesis replacement, Cheboksary

Ochronosis is a rare metabolic disease that occurs due to mutation of homogentisate 1,2-dioxygenase gene, and leads to accumulation of homogentisic acid (HTA) in the body. Affected by tyrosinase, circulating HTA converts into alkapton, part of which is excreted by kidneys, but the most of the pigment is deposited in cartilages and connective tissues. Ochronosis is characterized by three main symptoms occurring in a certain chronological order: since birth, it becomes noticeable that urine darkens when contacting with air, then, at the age of 20-30, ears and sclera become pigmented, and, in advanced stage of the disease, after 40, ochronotic spondilo- and arthropathy appear. The article reports about two clinical cases of the late diagnosis of ochronosis with the development and rapid progression of secondary osteoarthrosis (OA), which demanded consequent endoprosthesis replacement of two large joints in both patients. A feature that was found out while observing both patients was the reduction of the bone mineral density (BMD) in the proximal femur when it was “false normal” in the lumbar spine. In one case, the course of OA was complicated by the development of avascular necrosis of the femoral head. Late diagnosis of ochronosis makes it impossible to manage pathogenetic therapy just in time and inevitably leads to the curative treatment.

Key words: alkaptonuria, ochronosis, ochronotic arthropathy, secondary osteoarthrosis, avascular necrosis, osteoporosis, endoprosthesis replacement.
For citation: Bashkova I.B., Kichigin V.A., Shaipov R.Sh. et al. Ochronosis as a cause of secondary osteoarthrosis // RMJ. 2017. № 7. P. 474-480.