Is liver analysis still required for the diagnosis of primary hyperoxaluria type 2?

Failure of isolated kidney transplantation in a pediatric patient with primary hyperoxaluria type 2

PH type 2 is caused by decreased activity of GRHPR enzyme that eventually leads to ESRD and systemic oxalosis. Here, we describe an Iranian pediatric patient with PH2 and early ESRD development who received recommended treatment by undergoing isolated kidney transplantation. Diagnosis criteria included a history of reoccurring calcium oxalate renal stones and elevated oxalate levels combined with liver biopsy and decreased enzymatic activity at age five. ESRD prompted transplantation and was performed at age nine. On Day 12 post-op, his serum creatinine level increased. A graft biopsy showed calcium oxalate crystal deposits in renal tubes with no evidence of acute rejection, which resolved with intensive hydration and administration of a potassium citrate solution. Subsequent biopsies confirmed results found in first biopsy. Despite the immunosuppressive therapy, his serum creatinine level increased again after 11 months. Renal tubular obstruction then led to graft nephrectomy. Pathological analysis of tissue confirmed findings of past biopsies. This was a very rare case of early ESRD in PH2 resulting in a failed isolated kidney transplant. As the GRHPR enzyme is predominantly expressed in liver, we suggest a combined liver-kidney transplant may be beneficial in patients with PH2.

[Inherited monogenic kidney stone diseases: recent diagnostic and therapeutic advances]

Hereditary monogenic kidney stone diseases are rare diseases, since they account for nearly 2% of nephrolithiasis cases in adults and 10% in children. Most of them are severe, because they frequently are associated with nephrocalcinosis and lead to progressive impairment of renal function unless an early and appropriate etiologic treatment is instituted. Unfortunately, treatment is often lacking or started too late since they are often misdiagnosed or overlooked. The present review reports the genotypic and phenotypic characteristics of monogenic nephrolithiases, with special emphasis on the recent advances in the field of diagnosis and therapeutics. Monogenic stone diseases will be classified into three groups according to their mechanism: (1) inborn errors of the metabolism of oxalate (primary hyperoxalurias), uric acid (hereditary hyperuricemias) or other purines (2,8-dihydroxyadeninuria), which, in addition to stone formation, result in crystal deposition in the renal parenchyma; (2) congenital tubulopathies affecting the convoluted proximal tubule (such as Dent's disease, Lowe syndrome or hypophosphatemic rickets), the thick ascending limb of Henlé's loop (such as familial hypomagnesemia and Bartter's syndromes) or the distal past of the nephron (congenital distal tubular acidosis with or without hearing loss), which are frequently associated with nephrocalcinosis, phosphatic stones and extensive tubulointerstitial fibrosis; (3) cystinuria, an isolated defect in tubular reabsorption of cystine and dibasic aminoacids, which results only in the formation of stones but requires a cumbersome treatment. Analysis of stones appears of crucial value for the early diagnosis of these diseases, as in several of them the morphology and composition of stones is specific. In other cases, especially if nephrocalcinosis, phosphatic stones or proteinuria are present, the evaluation of blood and urine chemistry, especially with regard to calcium, phosphate and magnesium, is the key of diagnosis. Search for mutations is now increasingly performed in as much as genetic counselling is important for the detection of heterozygotes in autosomic recessive diseases and of carrier women in X-linked diseases. In conclusion, better awareness to the rare monogenic forms of nephrolithiasis and/or nephrocalcinosis should allow early diagnosis and treatment which are needed to prevent or substantially delay progression of end-stage renal disease. Analysis of every first stone both in children and in adults should never be neglected, in order to early detect unusual forms of nephrolithiasis requiring laboratory evaluation and deep etiologic treatment.