Renal function and kidney size in glycogen storage disease type I

Renal failure has been reported recently as a late complication of glycogen storage disease type I (GSD I). We studied the renal function of 23 patients, mean age 10.9 years (range 2.2-21.6 years). The mean glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were 188 +/- 50 and 927 +/- 292 ml/min per 1.73 m2, respectively (normal values for adult controls 90-145 and 327-697, respectively). Hyperfiltration (GFR greater than 145 ml/min per 1.73 m2) was found in 19 of 23 patients. There was no difference in GFR and ERPF between age groups 2-10 and 11-22 years. After a mean follow-up of 2.5 years (range 1-7.5 years) GFR and ERPF did not significantly change. At follow-up 3 patients (all older than 15 years) developed persistent glomerular proteinuria (0.1, 0.5 and 0.9 g/day). Besides a slight increase in fractional excretion of beta 2-microglobulin (FE-beta 2m) in 6 patients, proximal tubular function tests (FE-beta 2m, tubular reabsorption of phosphate and glucosuria) were normal. In patients with increased kidney length related to body height, GFR and ERPF were significantly higher than in patients with normal kidney length. We conclude that GSD I is characterised by hyperfiltration and hyperperfusion. The relative increment in kidney length is related to the degree of hyperfiltration.