Indian Journal of Rheumatology

: 2018  |  Volume : 13  |  Issue : 3  |  Page : 209--210


Dillibabu Ethiraj, Venkatraman Indiran, Kanakaraj Kannan, Thirumalasetty Ramachandra Prasad 
 Department of Radiology, Sree Balaji Medical College and Hospital, Chennai, Tamil Nadu, India

Correspondence Address:
Dr. Venkatraman Indiran
Department of Radiology, Sree Balaji Medical College and Hospital, Chennai - 600 044, Tamil Nadu


How to cite this article:
Ethiraj D, Indiran V, Kannan K, Prasad TR. Alkaptonuria.Indian J Rheumatol 2018;13:209-210

How to cite this URL:
Ethiraj D, Indiran V, Kannan K, Prasad TR. Alkaptonuria. Indian J Rheumatol [serial online] 2018 [cited 2022 Dec 8 ];13:209-210
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A 60-year-old male presented with bilateral knee pain and backache for the last 1 year, which was insidious in onset, nonradiating, progressive in nature, and associated with difficulty in walking. There was no history of trauma and relevant family history. He also reported brownish-to-black staining of undergarment. Physical examination showed mild restriction of movement in the spine and bilateral knee tenderness. Brownish-to-black discoloration was seen in both the ears. Radiographs of lumbar spine showed mild degenerative changes and osteoporosis of the spine. Disc calcification was seen at all lumbar and lower dorsal levels with vacuum phenomenon at lower dorsal intervertebral disc levels. Sacroiliac joint space was normal. Radiographs of both knee joints showed extensive degenerative changes involving both tibiofemoral and patellofemoral joints with global reduction of tibiofemoral joint spaces and bilateral loose bodies [Figure 1]. Ultrasound of supraspinatus, patella, quadriceps, and Achilles tendons showed thickening of tendons consistent with tendinosis and associated calcification in the distal tendons close to bony attachment [Figure 2]. The urine specimen had a dark, iron oxide-like discoloration when the urine specimen was kept in the sunlight. Gas chromatography/mass spectrometry of urine confirmed this case as alkaptonuria (AKU).{Figure 1}{Figure 2}

AKU is an uncommon inborn metabolic disorder due to a mutation in the homogentisic acid oxidase enzyme (HGO) gene on chromosome 3q. The worldwide prevalence of AKU is 1:250,000–1:1 million births.[1] As HGO is deficient in AKU patients, there is an accumulation of homogentisic acid in the blood and urine. Homogentisic acid gets deposited in the tendons, soft tissues, large joints, cartilages, and intervertebral discs space. Ochronotic pigment deposition in the ligaments and tendons starts in the second decade.[2] Symptoms usually start from the third or fourth decade of life. Hardening of ligaments, tendons, and muscles predispose them to rupture after minimal injury. According to the modified staging system by Jebaraj et al. for ochronosis of the spine, our patient falls under Stage 3 and Stage 4 of the disease. According to the radiological staging system by Jebaraj et al., normal spine/endplate sclerosis or early disc space changes represent Stage 1 and calcification of three or fewer intervertebral discs represent Stage 2 disease. Calcification of more than three intervertebral discs with sandwich spine appearance constitutes Stage 3 disease, and bony fusion of most of the segments of the thoracolumbar spine constitutes Stage 4.[2]

Ochronosis usually affects the dorsolumbar spine and typically spares the sacroiliac joints and cervical spine.[3] Plain radiographs have a poor role in diagnosing early tendonitis, but ultrasound examination can diagnose early tendonitis features such as tendon thickening and calcification, thereby prompting us toward an early workup.[4] There is no effective treatment currently for this inborn disorder. Nitisinone and high dose of Vitamin C are used nowadays. However, nitisinone is not yet fully licensed and high dose of Vitamin C is not very effective. Symptoms are managed by wax therapy, analgesics, and dietary restriction of tyrosine and phenylalanine. Joint replacement is usually done for end-stage joint disease.[1],[3]

Declaration of patient consent

The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.


We thank Prof. M. Prabakaran, Head of Radiodiagnosis, Sree Balaji Medical College and Hospital, for his guidance and valuable inputs in preparing this manuscript.

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Conflicts of interest

There are no conflicts of interest.


1Phornphutkul C, Introne WJ, Perry MB, Bernardini I, Murphey MD, Fitzpatrick DL, et al. Natural history of alkaptonuria. N Engl J Med 2002;347:2111-21.
2Jebaraj I, Chacko BR, Chiramel GK, Matthai T, Parameswaran A. A simplified staging system based on the radiological findings in different stages of ochronotic spondyloarthropathy. Indian J Radiol Imaging 2013;23:101-5.
3Baeva M, Bueno A, Dhimes P. AIRP best cases in radiologic-pathologic correlation: Ochronosis. Radiographics 2011;31:1163-7.
4Jebaraj I, Rao A. Achilles tendon enthesopathy in ochronosis. J Postgrad Med 2006;52:47-8.