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01-07-2016 | Clinical Quiz
An infant with nephrolithiasis and renal failure: Answers
Published in: Pediatric Nephrology | Issue 7/2016
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1.
2,8-Dihydroxyadenine (DHA) crystals
2.
Adenine phosphoribosyltransferase (ARPT) deficiency
Blood examination revealed anemia, severe impaired renal function, hyperuricemia, and hyperphosphatemia. The urinary sediment showed multiple spherical and reddish-brown particles with a dark outline and central spicules which are characteristic to 2,8-DHA crystals. Computed tomography showed multiple renal stones. Based on these findings, we diagnosed the patient with chronic kidney disease associated with APRT deficiency.
The diagnosis of APRT deficiency disease in our patient was made and confirmed by: (1) characterization of 2,8-DHA crystals in the urinary sediment; (2) sensitivity of proliferating T lymphocytes in response to an adenine analog, the cytotoxicity of which is dependent on APRT (T-cell method); (3) molecular analysis of the APRT gene.
Microscopic examination of the urinary sediment revealed multiple spherical and reddish-brown particles with a dark outline and central spicules that looked like “Maltese crosses” under polarized light. A semi-qualitative spectrophotometric analysis of the removed renal stones revealed a curve very similar to that of 2,8-DHA. The T-cell method showed that the patient was homozygous or compound heterozygous for an APRT gene mutation. Genetic analysis of the APRT gene confirmed the diagnosis of APRT deficiency and revealed a compound heterozygous state for p.M136T (APRT*J) and p.W98X (APRT*Q0).
In addition to APRT deficiency, the patient had left vesicoureteral reflux (grade III) and a right ureterocele, which was confirmed by voiding cystourethrogram. Medical therapy was started with allopurinol (10 mg/kg). The patient is now 24 months old and creatinine remains elevated (1.3 mg/dl).