Hypertrichosis lanuginosa acquisita (HLA), or malignant down, is a rare condition characterized by the appearance of lanugo hairs in generalized areas of skin. Lanugo hairs are fine hairs with little or no pigment and resemble the fine hair seen in some infants shortly after birth. HLA commonly affects skin sites with little to no hair growth, such as the nose and smooth, non-hair-bearing (glabrous) skin of the face.

HLA is classically associated with lung, breast, and colorectal carcinomas, but has been described in association with a variety of solid tumors. HLA due to internal malignancy shows a strong female predominance and typically occurs between the ages of 40-70 years. HLA may be accompanied by additional paraneoplastic signs or manifestations of internal disease, such as glossitis, taste disturbances, lymphadenopathy, acanthosis nigricans, and the sudden appearance of multiple seborrheic keratoses (ie, sign of Leser-Trélat).

Hair growth can occur up to 2.5 years before the malignancy is identified or up to 5 years after the cancer diagnosis. The etiology of tumor-associated HLA is presumed to be the result of a tumor-secreted product, though specific biochemical or hormonal causes have not been identified to date.