Kidney stone analysis may miss diagnoses as demonstrated by a case of adenine phosphoribosyl transferase deficiency

Fourier-transformed infrared (FTIR) spectroscopy is a frequently requested test in patients with kidney stones. It is considered particularly useful when routine stone urine screens do not identify any significant abnormalities. This case report describes a patient with undiagnosed adenine phosphoribosyltransferase (APRT) deficiency, a disorder presenting with kidney stones, who had initial symptoms at 16 months of age but no diagnosis until they were 6 years old. Initial investigations including a urine stone screen did not show significant abnormalities; however, FTIR analysis suggested the stones had a significant component identified as lansoprazole, a drug the patient was not taking. After repeated stone formation, urinary tract infections and inpatient stays, the disorder was identified incidentally during validation of a method for purine and pyrimidines in urine. This case highlights that FTIR analysis, although useful, has pitfalls and that other investigations are of equal value in reaching a diagnosis.