No abstract

Sirs, We read with great interest the letter of Demirdas and Schröder [1] about the differential diagnosis in changed color of urine in infants.We have followed a 3-month-old male who was hospitalized for the presence of orange-colored diapers. He was born from unrelated parents after an uneventful pregnancy. High levels of uric acid were found in the plasma (11.7 mg/dl; normal values 1.7-5.8). Kidney ultrasound examination showed mild and diffuse increase of signal in cortical area with nephrolithiasis. Fundus oculi, electroencephalogram (EEG), and brain ultrasound were normal. Successively, the infant presented dystonic movements, mild axial hypotonia, and hypertonia of the legs with increased tendon reflexes and scissoring. The study of purine and pyrimidine metabolism by electrospray ionization tandem mass spectrometry (MS-MS) showed high levels of hypoxanthine (20.3 mmol/mol of creatinine; normal values 0.43-11.31). Enzymatic assay in red cells showed an absence of hypoxanthine-guanine phosphoribosyltransferase activity (HGPRT). Molecular analysis confirmed the diagnosis of Lesch-Nyhan disease (LND; OMIM 300322) in the patient and his mother as a carrier: a duplication of 8 nucleotides 89-96 (89_96dupAGGATTTG) in exon 2 of HPRT1 gene was found in chromosome X.Brain magnetic resonance imaging showed white matter atrophy of bilateral symmetric temporal-insular regions with respective enlargement of subarachnoid spaces with mild decreased concentration of NAA and Cho at spectroscopy. At 20 months, the patient was unable to control his head or speak; he also showed swallowing and severe dystonic-dyskinetic movement disorder of the upper limbs with generalized hypertonia crisis towards opistotonus.