three cases of alkaptonuria in one family in mazandaran province, iran

background: alkaptonuria is a rare genetic disease leading to the accumulation of homogentesic acid in joint and ear cartilage, sclera and some other tissues causing significant morbidity in these patients. in this paper, we report three cases of alkaptonuria among the family or household members. case presentation: a 51-year-old man with mechanical low back and knee pain was referred to rheumatology clinic of babol university of medical sciences. the physical examination showed thoracic kyphosis and limitation of motion in thoraco-lumbar spine, severe knee osteoarthritis and blue-black discoloration of ear cartilages. there was intervertebral disc calcification in plain radiography, and mitral valve calcification in echocardiography. his urine sample was tested positive in benedict’s test. the diagnosis was confirmed by qualitative assessment of homogentesic acid (hga) that was highly positive. in addition, we found two more cases of alkaptonuria in his family. conclusion: although alkaptonuria is a rare disease, but it may be found in cluster among the family members.