Progressive nodular histiocytoma (PNH) is a rare, progressive disease characterized by the widespread eruption of yellow-brown papules, plaques, and nodules. Lesions are both superficial and deep. The face and mucous membranes may be affected while flexors are often spared. Papules are randomly scattered, while nodules are more likely to be found on the trunk.

Patients aged 40-60 are most commonly affected, but PNH may present at any age. There are no definitive associations with other diseases. Nodule histiocytes may accumulate iron, and PNH has been anecdotally associated with iron-deficiency anemia.

PNH is a type of non-Langerhans cell histiocytosis. It is not associated with Langerhans histiocytosis or abnormal serum lipids. Histologically, juvenile xanthogranuloma and PNH share many characteristics.

PNH lesions may be very painful; ulceration and bleeding may occur. There is no spontaneous remission, and new lesions continue to arise throughout the disease course. Management of skin lesions is notoriously difficult; multiple surgeries may be necessary. That being said, PNH is not associated with any visceral changes.