A Mimic of Ankylosing Spondylitis, Ochronosis: Case Report and Review of the Literature

AbstractPurpose of ReviewOchronosis and alkaptonuria are manifestations of the same condition —a rare autosomal recessive disorder resulting from a constitutional lack of homogentisate 1,2-dioxygenase (HGD) with the consequent accumulation of homogentisic acid (HGA). In ochronosis, HGA undergoes autoxidation as well as enzymatic oxidation to form an ochronotic pigment that accumulates in c artilage and connective tissues. In the beginning, there is homogentisic aciduria and pigmentation of cartilages and other connective tissues. In later years, generalized osteoarthritis of the spine and large joints, termed ochronotic arthropathy, develops.Recent FindingsThe diagnosis is confirmed by quantitative measurement of HGA in urine and mutation analysis of the HGD gene. One of the differential diagnoses for the skin findings is exogenous ochronosis, a limited hyperpigmentation of skin caused by some chemicals. As for the lumbar spine findings, there can be radiographic similarities with ankylosing spondylitis (AS) including reduced intervertebral disc spaces and loss of lumbar lordosis; however, ochronosis will spare the sacroiliac joint, and the lumbar spine will show dense, wafer-like disk calcification with a vacuum disc phenomenon and broad syndesmophytes.SummaryHere, we present a case of a patient with probable ochronosis that was treated many years as ankylosing spondylitis without response, and we provide a review of the current literature on ochronosis pathogenesis, diagn...

Source: Current Allergy and Asthma Reports - March 5, 2021 Category: Allergy & Immunology Source Type: research