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Paper text:
alkaptonuria is a rare autosomal recessive disease , resulting from deficiency of the enzyme homogentisic acid oxidase , which is involved in the metabolism of phenylalanine and tyrosine aminoacids .
due to partial or total deficiency of homogentisic acid oxidase in the liver and kidneys , homogentisic acid accumulates in blood , part being excreted in the urine . on exposure to the atmosphere
it is also reported to be deposited in the skin , tympanic membrane , heart valves , sclera , cartilages of nose and ears , kidneys , pancreas , and large vessels . due to accumulation of homogentisic acid
, cartilages get a dark discoloration and become brittle and more vulnerable to mechanical stress .
the development of degenerative arthritis with accompanying brownish black pigmentation of the tissues and dark discoloration of the urine is called  ochronosis . 
clinical diagnosis is made on the basis of skeletal manifestations including lower back pain , stiffness , and degenerative arthropathy of the large joints , ochronotic pigmentation of the tissues and blueish black discoloration of urine .
the definitive diagnosis of the alkaptonuria may be confirmed with several biochemical tests for the quantitative presence of homogentisic acid in urine .
since there is no effective medical treatment for alkaptonuria , treatment at present is symptomatic by local heat , physiotherapy , analgesics , external support and with surgical treatment in the form of synovectomy , arthroscopic debridement , fusion , or arthroplasty as indicated regarding the affected joint .
we present a patient who was diagnosed to have alkaptonuria during further laboratory tests after observing ochronotic brownish black pigmentation of the menisci and femoral cartilage during arthroscopy of the knee .
a 30-year - old woman presented with complaints of pain in the left knee along with occasional episodes of locking for 1 year .
her physical examination revealed tenderness on the medial joint line and positive mcmurray 's test .
ordinary x - ray images of the knees were found to be normal . magnetic resonance imaging ( mri ) of the left knee revealed bucket handle tear of medial meniscus along with partial tear of anterior cruciate ligament .
she was planned for arthroscopic partial meniscectomy in view of her complaints and mri findings . during the arthroscopic examination of her left knee joint
there was mild synovial hypertrophy and a bucket handle tear was found in the medial meniscus that appeared to be brownish black in color [ figures 1 , 2 ] .
meniscectomy for bucket handle tear of medial meniscus was done and specimen was sent for histopathological examination .
excised medial meniscus showing brownish black discoloration excised medial meniscus ( under surface ) further investigations were planned for the diagnosis of ochronosis considering discoloration of the joint cartilage and menisci .
the patient 's freshly passed urine turned dark brown after addition of sodium hydroxide to the sample to facilitate oxidation .
histopathological examination of the excised tissue showed pigmentation and degenerative changes [ figure 3 ] .
no pathological findings were detected with the detailed examination of the ear , sclera , skin , and cardiovascular system .
further treatment was done in the form of physiotherapy and by administering vitamin c and analgesics .
after the medical and surgical treatment , the patient 's complaints were alleviated and no complaints were registered , during the next follow - up .
few reports of arthroscopic diagnosis and treatment of ochronosis have been found in the literature .
chen et al . reported the arthroscopic findings of a 50-year - old male patient who was complaining of pain in both knees .
reported the arthroscopic findings of a 40-year - old man who had arthroscopy of the knee and shoulder and kural et al . presented a 50-year - old woman in whom arthroscopic examination of the right knee revealed brownish black discoloration of the articular cartilage and menisci leading to the diagnosis of alkaptonuria by further laboratory examinations .
generalized synovial hypertrophy accompanying brownish black discoloration of articular cartilage and menisci were our common arthroscopic findings with other reported cases in the literature .
generalized cartilage degeneration was not present in our case probably due to comparatively younger age of our patient .
in our case there was an additional meniscus tear unlike in that of thacker 's case and similar with chen 's , kural 's and raaijmaaker 's case .
similar to raaijmaaker 's case arthroscopy was a diagnostic and treatment tool to remind us of ochronosis and direct us for further research . during arthroscopy ,
brownish black discoloration of the articular cartilage and menisci warned us to have further research for ochronosis .
macroscopic examination of the urine following alkalization and positive ferric chloride test further established our diagnosis .
but we were not able to perform the laboratory tests that determine the level of homogentisic acid in urine and blood due to higher cost involved in these tests .
approximately 50% of the alkaptonuric patients manifest one clinical form of ochronosis after the fourth decade .
diagnosis can be made during childhood by observing dark coloration of diapers or urine when left standing .
our patient 's mother had noticed the dark color of her urine in early childhood .
ochronotic discoloration of the cartilage of the ears and nose may be observed at the age of 30 .
other less common extra articular manifestations are ochronosis of the heart with valve stenosis and urinary tract obstruction by ochronotic calculi .
treatment with high dose of ascorbic acid proved to lower the levels of homogentisic acid in excreted urine , but does not prevent the occurrence of arthropathy .
nitisinone is shown to have significantly altered the excretion of homogentisic acid in urine in both human and rat studies .
nitisinone is suggested to be used for treatment of the tyrosinemia type 1 but its use in ochronotic patients has yet to be proved .
since there is no effective treatment to replace the deficient enzyme , symptomatic treatment is initiated with nsaids , intra - articular steroid injection and ascorbic acid .
arthroscopic debridement , synovectomy , partial , or total joint arthroplasties and fusion are the surgical treatment options .
. raaijmaakers et al . reported to provide symptomatic relief with administering 400 mg / day chondroitin sulfate and 1500 mg / day glucosamine for 4 months .
finally , ochronosis is a rare metabolic disorder affecting peripheral joints as well as spine and the soft tissues and arthroscopy has great importance in suspecting and diagnosing ochronosis .
ochronotic arthropathy is a rare condition found in patients with alkaptonuria , which is a hereditary metabolic disease associated with deposition the of homogentisic acid derivatives in various connective tissues of the body . 
 we present the case of a 30-year - old woman in whom arthroscopic examination of the left knee prior to meniscectomy for bucket handle tear of medial meniscus revealed brown - black discoloration of the articular cartilage and menisci leading to the diagnosis of alkaptonuria by further laboratory evaluation . after medical and surgical treatment , 
 patient 's complaints were alleviated and no further complaints were registered , during the next follow - up .