OBJECTIVE: To investigate the clinical significance of serum Cyst-C and urinary microalbumin in early renal impairment in children with Henoch-Schonlein purpura (HSP). METHODS: Forty-eight children with HSP and who had normal serum creatinine level and 31 healthy children were enrolled. Contents of serum Cyst-C and urinary microalbumin were measured using ELISA and immunoturbidimetry, respectively. Urinary routine examination was performed in children with HSP. The contents of serum Cyst-C and urinary microalbumin were re-examined one month after treatment (recovery phase). RESULTS: The contents of serum Cyst-C (2.24±0.81 mg/L) and urinary microalbumin (20.04±10.32 mg/L) in the HSP group at the acute phase were significantly higher than those in the control (0.85±0.20 and 2.30±1.38 mg/L respectively; P<0.01). Serum Cyst-C (1.70±0.30 mg/L) and urinary microalbumin contents (13.20±8.16 mg/L) were significantly reduced at the recovery phase compared with those at the acute phase in the HSP group (P<0.01). The proportion of urinary routine abnormality (33.3%) was significantly lower than that of urinary microalbumin (68.8%) and serum Cyst-C abnormalities (72.9%) in the HSP group (P<0.01). CONCLUSIONS: Serum Cyst-C and urinary microalbumin may serve as indexes in the assessment of early renal impairment in children with HSP.［Chin J Contemp Pediatr, 2009, 11 (5):346-348］