FLT4 and disorder of glycogen metabolism: In GSD patients, it has been shown that lymphatic vascular endothelial hyaluronan markers are present on endothelial cells,[13] and the levels of circulating platelet-derived growth factor-BB, which promotes lymphangiogenesis, are elevated.[14] The endothelial cells express VEGF receptors, especially VEGF receptors-3, which is activated by VEGF-C, VEGF-A, and VEGF-D promoting angiogenesis and lymphangiogenesis in the bone marrow of GSD patients.[15,16] As a result, bone resorption might be caused by mechanical compression of abnormal lymphangiomatous tissue.