[Renal impairment in patients with methylmalonic aciduria: a review of five cases].

Objective: The renal impairment in children with methylmalonic aciduria has seldom been reported. To improve knowledge in this aspect, clinical data of five cases with methylmalonic aciduria with renal involvement were analyzed and the results are reported in this paper, which may be of some help in early diagnosis, treatment and in achieving favorable prognosis.

Methods: Urine methylmalonic acid was measured by gas chromatography-mass spectrometry analysis, if the content exceeded the normal range and vitamin B12 deficiency was excluded, the diagnosis of methylmalonic aciduria was confirmed. Homocysteine in plasma was also measured with fluorescence polarization immunoassay to make sure if concomitant homocysteinemia existed. From January 2002 to January 2005, five patients who had renal impairment were diagnosed as methylmalonic aciduria by urinary organic acid analysis. Among them, three were male, two were female, aged from seven months to 26 years, with average of 13 years. Three were presented to pediatric nephrology clinic with hematuria, proteinuria or edema, the other two were presented to pediatric neurology clinic first for psychomotor retardation. Their clinical features, laboratory findings, treatment regimens and prognosis were analyzed and summarized.

Results: All the five patients with methylmalonic aciduria were found to have various degrees of renal impairment, manifested as hematuria or proteinuria. Among them, two cases had gross hematuria and three had microscopic hematuria. Edema was found in two cases and hypertension occurred in one case. Early indicators of renal damage, such as microalbunminuria, N-acetyl-beta-D glucosaminidase, transferrin and alpha-microglobulin showed glomerular and tubular dysfunction. Clinically nephrotic syndrome was diagnosed in one case, the other four cases were diagnosed as glomerulonephritis, and two cases had renal failure. Renal biopsy was performed in one case, tubulo-interstitial damage and mesangial proliferation appeared. Mental retardation and psychomotor disorder were chief nervous system complaints. Leukodystrophy was the main finding on imaging. Megaloblastic anemia was found in three cases. All the five patients were cobalamin-responsive type. Renal impairment was alleviated following treatment, edema and gross hematuria as well as hypertension disappeared later, proteinuria diminished, renal function improved, central nervous system symptoms and hematopoietic function ameliorated.

Conclusion: In patients with hematuria, proteinuria or renal failure of unknown origin, metabolic screening and urinary organic acid analysis should be performed as early as possible to confirm the diagnosis.