Coexistence of ochronosis and rheumatoid arthritis

Inflammatory rheumatic diseases in patients with ochronotic arthropathy

BACKGROUND

Ochronotic arthropathy (OcA) refers to excessive homogentisic acid (HGA) deposition in the musculoskeletal system. Our current understanding of OcA is limited, as there are less than a thousand alkaptonuria (AKU) cases reported in the literature. Herein, we investigated the rheumatological manifestations of OcA in a group of adult AKU patients.

METHODS

Adult AKU patients with symptoms suggestive of OcA were included. Patients underwent a detailed rheumatological assessment. Laboratory testing, including autoantibodies and radiological investigations such as conventional X-rays, and magnetic resonance imaging (MRI) were performed.

RESULTS

Eight out of 12 (66%) patients had symptoms consistent with OcA. The median age at OcA symptoms was 36 (27-48) years, and the presenting symptom was back pain in 87.5% of the patients. All patients had chronic back pain, and three (37.5%) had an inflammatory type of pain character. Radiographic sacroiliitis based on X-rays was present in 2 (25%) cases. MRI of the sacroiliac joints documented bone marrow edema in five (62.5%), and spinal MRI identified corner inflammatory lesions in three patients (37.5%). One patient (12.5%) had rheumatoid arthritis. Extra-articular involvement, including enthesitis (n = 1; 12.5%), interstitial lung disease (n = 1; 12.5%), and scleritis (n = 1; 12.5%), was also noted.

CONCLUSION

The frequent occurrence of OcA-related inflammatory manifestations in our patients contradicts the conventional concept of OcA as a non-inflammatory disorder. The activation of inflammatory pathways, possibly by the HGA products, may responsible for this condition.Significance and innovationsAbout three-fourths of adult ochronotic arthropathy (OcA) patients in our group had associated inflammatory disease.OcA associated inflammatory diseases were showing a severe phenotypeNearly half of the OcA patients required early prosthesis operations compared to their healthy counterparts.

Alkaptonuric ochronosis with aortic valve and joint replacements and femoral fracture: a case report and literature review

Alkaptonuria is a rare autosomal recessive disorder of metabolism caused by deficiency of homogentisic acid oxidase and resulting in accumulation of homogentisic acid in collagenous structures. It is characterized by homogentisic aciduria, bluish-black discoloration of connective tissues (ochronosis) and arthropathy of large joints. Less common manifestations include cardiovascular abnormalities, renal, urethral and prostate calculi. Bone fractures are unusual in ochronosis. In this report, we describe a woman, 69 years of age, with a history of dark urine since childhood and progressive pigmentation of the skin, sclera, and auricular cartilages. She had severe arthropathy requiring total joint replacement in both of her knees and right hip. She also had severe aortic stenosis requiring valve replacement, and asymptomatic nephrolithiasis. She presented with a low trauma fracture of the distal femur despite two years of alendroate therapy. We review the etiology, pathogenesis, clinical presentation, diagnosis and treatment of alkaptonuric ochronosis. Early detection is important for prevention and treatment of multiple systems. Nitisinone, a potent inhibitor of 4-hydroxyphenylpyruvate dioxygenase, dramatically reduces production and urinary excretion of homogentisic acid; however, the long-term efficacy and side effects of such therapy are unknown. Identifying the gene for alkaptonuria offers the potential for a new therapeutic approach (replacement therapy with a recombinant enzyme) in the treatment of alkaptonuric ochronosis.