Intralymphatic histiocytosis (IH) is a rare reactive cutaneous condition characterized by macrophage accumulation in dermal lymphatic vessels.

IH typically presents as an asymptomatic pink, reddish, or violaceous macule or thin plaque, usually on an extremity. The erythema may wax and wane. A livedo-like appearance has frequently been reported. Overlying papules and nodules may be seen. Rarely, IH presents with edema without erythema. Uncommon lesion locations include eyelids, larynx, external genitalia, breasts, and oral mucosa.

The majority of reported patients are female and, while a broad age range is affected, most cases occur after the age of 60.

IH may be primary or, more frequently, may be associated with an underlying systemic disease. The majority of reported patients have rheumatoid arthritis (RA). Metal joint implantation, severe osteoarthritis, and malignancy (breast, colon, and Merkel cell cancers) are also reported associations.

While the etiology of IH is unclear, chronic inflammation and lymphostasis are thought to be contributory factors.