#2633 Navigating complexity: a case report of chronic kidney disease with renal stone unravelling a rare metabolic disorder

Abstract

Abstract Clinical Presentation A 48-year-old female of Asian heritage was referred for renal assessment after experiencing recurrent acute kidney injury (AKI) with incomplete recovery between episodes. This was initially attributed to dehydration and interstitial nephritis stemming from long-standing vomiting, a manifestation of gastroscopy-proven erosive gastritis, compounded by the use of high-dose proton pump inhibitors (PPI). Her relevant medical history is of right nephrectomy in 1996 due to recurrent urinary tract infections (UTIs), and previous left renal calculus in 2019 with no visible stones on further CT imaging. Despite living with a single kidney, her baseline eGFR had been normal prior to referral. While unaware of her mother's medical history, her father was recently diagnosed with kidney disease (no clear history) and her sister Wilson's disease. A kidney biopsy was undertaken given the incomplete eGFR recovery between episodes. The biopsy revealed adequate tissue including 24 glomeruli, no significant glomerular pathology was seen. There is 65% tubulointerstitial atrophy and fibrosis, and yellow to red-brown-tinged crystals within tubular lumina and epithelial cells, prompting a histiocytic reaction. These crystals were birefringent under polarized light and did not stain with Perl's and Von Kossa stain (Fig. 1a-d). Immunofluorescence was negative for all immunoglobulins and complement fractions. No immune complex/substructure deposits were seen in the glomeruli on electron microscopy. Blood tests assessing APRT activity indicated values within the carrier range (Table 1). The patient and her family have been referred for a comprehensive genetic testing for APRT genetic mutations. Treatment with Allopurinol 300 mg daily resulted in a sustained eGFR improvement from 19 to 33 ml/min/1.73m2 at 6 months after initiation (Fig. 1). Discussion Adenine phosphoribosyl transferase (APRT) deficiency, also known as Dihydroxyadenineuria, is a rare autosomal recessive inherited condition leading to kidney stones. If left untreated, up to 25% progress to end-stage kidney disease (ESKD). Although inherited, half of patient present in adulthood and may do so with laboratory findings of CKD rather than specifically with stones [1]. This case highlights the significance of precise diagnosis in calculi-related kidney diseases. Early intervention can alter the trajectory of specific conditions, averting progression to ESKD. This case is unusual in being a carrier of an autosomal recessive condition presenting with full manifestations of the disease. Patient Consent The patient has given verbal, documented consent for case publication. Acknowledgment We thank all renal and pathology staff members at Salford Care Organisation who contributed to the diagnosis and management of our case.