Distribution of TPO gene expression between liver, kidney, and spleen. Boxes indicate the median (straight line) with 25th and 75th percentiles. In addition, error bars with 10th and 90th percentiles, outliers (circles), and mean value (dotted line) are shown. The fractional amount of TPO gene expression in liver was significantly higher than in kidney or in spleen (P < .001), while kidney and spleen did not differ significantly (P = .12). Only one patient showed TPO mRNA expression below 80% in the liver and above 20% in the kidneys.