Background Alkaptonuria (AKU) is the first genetic metabolic disorder following an autosomal recessive pattern of inheritance, identified by Sir Achibald Edward Garrod (1). It is caused by a mutation in the HGD gene coding for the enzyme homogentisate 1,2-dioxygenase (E.C:184.108.40.206). The natural substrate of the enzyme, the homogentisic acid, is then accumulated in the blood and tissues, oxidated in a form called alkapton and then partially excreted in the urine, giving it an unusually dark color after it is exposed to the air. The excess of homogentisic acid causes damages to connective tissues with dramatic consequences as osteoarthritis and heart valves problems, with subsequent joint and valves replacement, stones in kidney and other organs are affected too. Usually symptoms develop in people after the third decade of age, and this make the disorder undervalued even though the dark discoloration of the urine is present from birth. AKU is a very rare disease, since its prevalence is 1-9/1 000 000 (Orphanet) and, at the moment, without a definite cure.
Objectives To evaluate the age at which AKU patients have been diagnosed, since on the basis of our experience the highest number of the adults received the exact diagnosis of AKU only late in age, after a long way looking for a resolution of their pain problems.
Methods To evaluate the age at which AKU patients have been diagnosed, since on the basis of our experience the highest number of the adults received the exact diagnosis of AKU only late in age, after a long way looking for a resolution of their pain problems.
Results The mean age of the patient was 50.1±17.3. Only 5 of them were diagnosed at the birth, the majority of the others (15) received the diagnosis between 40 and 58 years. The earliest diagnosis dates back to 1971, and in total 11 patients were diagnosed up to 1996, while 13 of them were diagnosed between 2004 and 2014. Apart from the mother's curiosity about the darkness of nappies which, however, did not always lead to a quick resolution, the physical difficulties leading patients to the diagnosis were different, but often due to rheumatic and orthopedic problems (back pain, arthroscopy, junction replacement, etc).
Conclusions Although the age of the diagnosis is decreased in the new century, too many people suffer without knowing to be affected by AKU. We hope the rheumatologists will play attention in considering AKU in their diagnosis and share the information with their colleagues like pediatricians, orthopedists, etc.
A.B. Garrod The Incidence of Alkaptonuria: a Study in Chemical Individuality Lancet, vol ii, pag. 1616-1620, 1902.
Disclosure of Interest None declared