Lymphangitis

Besides the veins, the body has another network of very fine tubing, the lymphatic vessels, through which the fluid from the tissues makes its way back. Lymphangitis is inflammation of those vessels, and it can show up as a complication of cellulitis, which is a bacterial infection of the skin.

The story starts with a break in the skin: a cut, a crack, a bite. That is where the bacteria get in, and the lesion spreads along the lymphatic vessels toward the lymph nodes.

That is what makes it look so distinctive. In erysipelas, another skin infection, when the vessels involved are the most superficial ones, the ones running just under the skin, the path shows up on the skin as a streak. It is literally the fluid's route back, traced on the skin.

It is important not to confuse it with a similar-sounding word. Lymphadenitis is not inflammation of the vessels but infection of the lymph nodes, which are the structures that filter lymph.