Publication:

Skin pigmentation, a window to diagnose Alkaptonuria: a very rare entity

Alkaptonuria (AKU) or endogenous ochronosis is a very rare inborn error of tyrosine metabolism inherited by autosomal recessive mode. There is complete absence of homogentisic acid oxidase enzyme which results in accumulation of homogentisic acid in cartilaginous connective tissue thus produces ochronotic clinical manifestations. Here we reported a 36 year old woman with bluish pigmentation of pinnae, index fingers (lateral aspect), nails, teeth and sclera. Detailed clinical and investigative workup was done to diagnose patient. Skin biopsy showed changes of ochronosis and urine examination revealed detectable level of homogentisic acid. Classical ocular findings, ochronosis on clinical and HPE and positive urinary tests for homogentisic acid confirmed the diagnosis of alkaptonuria. The highlight of our case is that an asymptomatic patient was detected early by ochronosis prior to development of musculoskeletal or cardiac complications.