[Features of proteinuria in Chinese male patients with Alport syndrome]

To explore the timing and course of proteinuria in Chinese patients with Alport syndrome (AS).This retrospectively study included 118 unrelated male AS patients at Department of Pediatrics, Peking University First Hospital between 1994 and 2009. The clinical data of the onset age of proteinuria, the degree of proteinuria and the prevalence of microalbuminuria were analyzed. Urinary total protein was detected by the pyrogallol red protein dye-binding assay, urinary microalbumin by immunoturbidimetric assay and urinary creatinine level by alkaline kinetics. Microalbuminuria was detected when the microalbumin: creatinine ratio was30 mg/g on a single random midstream first morning urine sample.A total of 106 patients had proteinuria. The occurring or detecting age of proteinuria varied from 1 month to 27 years. Five patients (4.7%) were under 1 year of age and 15 patients (14.2%) at toddler's age. Among 43 cases with nephrotic-level proteinuria, 21 cases (48.8%) presented with nephrotic-level proteinuria at age 6 - 12 year. Both urine total protein and morning urine microalbumin measurements within 7 days were made in 53 patients. Microalbuminuria occurred in 4 of 5 patients with normal daily urinary protein excretion. All 48 patients had daily proteinuria0.15 g. Increased urinary microalbumin was detected in 4 of 5 patients with normal daily urinary protein excretion and 46 patients with daily proteinuria0.15 g. The consistency of urine microalbumin concentration and urine microalbumin-to-creatinine ratio was excellent in 51 patients. However, in 2 patients with slightly increased daily urine total protein, urine microalbumin concentration was normal while the urine microalbumin-to-creatinine ratio abnormal (30 mg/g).In AS males, proteinuria occurs earlier and progresses rapidly. Since microalbuminuria precedes the onset of proteinuria, either urine microalbumin concentration or urine microalbumin-to-creatinine ratio in morning specimens should be used for detecting microalbuminuria. And microalbuminuria may serve as an early endpoint in intervention trials.