Alcaptonúria: odisseia diagnóstica revelando uma rara doença metabólica hereditária

Abstract

INTRODUCTION: Alkaptonuria is a rare autosomal recessive disorder due to the deficiency of the enzyme homogentisic-oxidase, produced by the liver and kidneys, which is involved in phenylalanine and tyrosine metabolism. In the absence of this enzyme, the accumulation of ochronous pigment occurs. The most important clinical manifestations of ochronosis are arthropathy, ocular and cutaneous pigmentation, dark urine and cardiovascular involvement. Nitisinone (NTBC) is a benzoylcyclohexane-1,3-dione that reversibly inhibits the activity of the enzyme step immediately before the homogenized dioxygenase, thereby reducing the production of homogentisic acid (HGA). Thus, it is considered that nitisinone may be a potential treatment for alcaptonuria. Here we report the first Brazilian patient treated with NTBC after a misdiagnosis of congenital porphyria. CASE REPORT: Male patient, referred for evaluation of urine darkening at two years of age, was diagnosed with alkaptonuria at 3 years of age. At 8 years of age, he was started on NTBC therapy with markedly homogentisic acid decrease. Tyrosine increase and ocular pain were noticed and were managed reducing NTBC dosage. DISCUSSION: Although considered a typically adult disease, the symptoms of alkaptonuria begin in childhood and have a progressive and devastating course. Early diagnosis of this disease allows the implementation of therapeutic measures, such as the use of NTBC, preventing the progression of disease manifestations and the appearance of irreversible sequelae.