DECREASED PLATELET COUNTS AND DECREASED PLATELET SEROTONIN IN POSTSTREPTOCOCCAL NEPHRITIS

Mean platelet survival time in patients with acute poststreptococcal g lomerulo-nephritis (APSGN) is reduced to 50-60% of the control values, and glomerular deposits of platelet factor 4 are found in these patie nts. In order to investigate further systemic platelet changes of path ogenic, clinical or prognostic significance, we measured the platelet serotonin (5-HT) content and the blood platelet counts during the Ist week of the disease in 27 patients with APSGN. Platelet 5-HT was signi ficantly reduced in patients with APSGN as compared with patients with impetigo without glomerular involvement (785+/-54 vs. 1,329+/-94 ng 5 -HT/10(9) platelets; p<0.001). Similarly, the mean blood platelet coun t was reduced to 247+/-16x10(3) as compared with 303+/-14x10(3) in the controls (p<0.05). Thirteen (48%) of these patients had individual va lues of platelet 5-HT lower than the 95% confidence interval calculate d in the control group. No significant correlation was observed betwee n the concentration of 5-HT and either the severity of the disease jud ged by the amount of urinary protein excretion and the serum creatinin e value or the presence of circulating immune complexes. Significant c orrection of the platelet 5-HT content (to 1,180+/-111 ng/10(9) platel ets; p<0.01) and of the platelet counts (to 309+/-21x10(3); p<0.01) we re observed in the longitudinal study at least 2 weeks later. Platelet activation, with secretion of granular content and increased consumpt ion, may explain these findings. Additionally, the reduced mean age of the circulating platelets could contribute to their decreased 5-HT le vels. The reduced platelet counts are not of clinical significance, bu t serial measurements of platelet 5-HT may be useful in predicting act ive glomerular inflammation.