Serum vascular endothelial growth factor D (VEGF-D), a biomarker of LAM disease, correlates with disease severity and can reflect the therapeutic effect of rapamycin in LAM patients (5), but controversy remains regarding the correlation between decreased VEGF-D and improved pulmonary function in sirolimus-treated patients (5, 6), and some LAM patients have normal serum VEGF-D concentrations (7). Here, VEGFD is linked to lymphangioleiomyomatosis.