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Dihydropyrimidinase deficiency is a rare autosomal recessive disease affecting the second step of pyrimidine degradation. It is caused by mutations in the DPYS gene. Only approximately 30 cases have been reported to date, with a phenotypical variability ranging from asymptomatic to severe neurological illness. We report a case of dihydropyrimidinase deficiency incidentally detected by urine metabolome analysis. Gas chromatography-mass spectrometry-based urine metabolomics demonstrated significant elevations of dihydrouracil and dihydrothymine, which were subsequently confirmed by a quantitative analysis using liquid chromatography-tandem mass spectrometry. Genetic testing of the DPYS gene revealed two mutations: a novel mutation (c.175G > T) and a previously reported mutation (c.1469G > A). Dihydropyrimidinase deficiency is probably underdiagnosed, considering its wide phenotypical variability, nonspecific neurological presentations, and an estimated prevalence of 2/20,000. As severe 5-fluorouracil-associated toxicity has been reported in patients and carriers of congenital pyrimidine metabolic disorders, urinary pyrimidine analysis should be considered for those who will undergo 5-fluorouracil treatment.

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BACKGROUND: Adenylosuccinate lyase (ADSL) deficiency is a defect of purine metabolism affecting purinosome assembly and reducing metabolite fluxes through purine de novo synthesis and purine nucleotide recycling pathways. The disorder shows a wide spectrum of symptoms from slowly to rapidly progressing forms. The most severe form is characterized by neonatal encephalopathy, absence of spontaneous movement, respiratory failure, intractable seizures, and early death within the first weeks of life. More commonly, ADSL presents purely neurologic clinical picture characterized by severe psychomotor retardation, microcephaly, early onset of seizures, and autistic features (type I) or a more slowly progressing form with later onset, and major features including slight to moderate psychomotor retardation, and transient contact disturbances (type II). Diagnostic markers are the presence of succinylaminoimidazole carboxamide riboside (SAICAr) and succinyladenosine (SAdo) in extracellular fluids. ADSL is a rare disorder, although its prevalence remains unknown. Of note, the wide range of essentially nonspecific manifestations and lack of awareness of the condition often prevent diagnosis. CASE PRESENTATION: We present here the case of particularly mild, late onset ADSL that has been unsuccessfully investigated until whole exome sequencing (WES) was performed. CONCLUSIONS: Besides emphasizing the valuable diagnostic value of WES, this report provides new data further documenting the relatively wide clinical manifestation of ADSL.

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A patient with molybdenum cofactor deficiency (producing the biochemical abnormalities associated with deficiencies of sulphite oxidase and xanthine dehydrogenase) clinically expressed Marfan-like habitus with dislocated lenses, vertebral abnormality, learning disability, moderate hemiplegia, increased medial lentiform MRI signal and intermittent microscopic haematuria. S-Sulphocysteine was present in plasma and urine, and the oxidized derivative of a molybdopterin precursor (precursor Z), together with xanthine and hypoxanthine, were elevated in urine. Blood uric acid was < 1 mg/dl, while urinary urothione was not detected. These data indicate a functionally inadequate terminal enzyme for converting precursor Z to active molybdopterin (complementation group B of general molybdenum cofactor deficiency). Although the biochemical parameters were indicative of a severe deficiency state, the patient has survived into the third decade with a less severe clinical spectrum than has generally been associated with this disease.

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In 24 patients with gout and in 15 patients with clinical oligo- and polyarthritic syndromes associated with hyperuricemia and dyspurinia xeroradiographic examinations of the clinically affected joints and soft tissues were carried out. In 32 cases comparisons were made with the classic x-ray examinations. In most cases the findings correlated, particularly the rarifaction of the bone structure including cystic changes of fingers and toes. In advanced cases, particularly in the hallux, erosions occurred and at the same time the changes in the soft tissues were recorded. Cystic changes in the larger bones were better estimated by the classical x-ray examinations. The soft tissues are shown better xeroradiographically. Xeroradiography has the advantage that it can record the structure of bones and soft tissue at the same time.

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