Alkaptonuric Ochronosis Superimposed With Septic Arthritis in A Middle-Aged Man

Alkaptonuria is a rare inborn metabolic disease, in which an enzymatic deficiency accumulates alkapton in different tissues, causing darkness and injury, especially in spine and large cartilages, called ochronosis. the urine darkness can be a key to early diagnosis in childhood, but some cases are missed until adulthood and gradual damage to cartilages causes disability and impairs the patients rsquo; quality of life. here, a 49year old male patient is presented with a 2 week history of left knee pain and swelling, who underwent arthrotomy, and the macro and microscopic evaluation revealed ochronosis, superimposed by septic arthritis. diagnosis of this rare disease should be considered in differential diagnoses of common joint disorders, like septic arthritis and osteoarthritis, so that appropriate management of the disease can prevent further damages.