Microlymphatics of human skin.

Microlymphatics of human skin form two superposed networks. The superficial one located at the level of dermal papillae may be visualized by fluorescence microlymphography. Microlymphatics fill from a subepidermal depot of minute amounts of FITC-dextran 150,000. In primary lymphedema with late onset the depicted network with vessels of normal size is significantly larger than in healthy controls, whereas in congenital lymphedema (Milroy's disease) microlymphatics are aplastic or ectatic (diameter > 90 microns). Lymphatic microangiopathy with obliterations of microvessels develops in chronic venous insufficiency, in lipedema (preliminary results) and after recurrent erysipelata. In healthy controls microlymphatics are permeable to FITC-dextran 40,000 and impermeable to the larger molecule 150,000. Preserved fragments of the network in chronic venous insufficiency exhibit increased permeability to FITC-dextran 150,000. After visualization of the vessels by the fluorescent dye microlymphatic pressure may be measured by the servo-nulling technique. First results indicate that microlymphatic hypertension contributes to edema formation in patients with primary lymphedema.