Unmasking the Face of a Rare Disease – Progressive Nodular Histiocytosis

Non-Langerhans cell histiocytoses (NLCHs) are a complex group of disorders which can be difficult to diagnose due to their confounding clinical and microscopic features. Progressive nodular histiocytosis (PNH) is a rare subtype of NLCH characterized by benign, xanthogranulomatous lesions on the skin and mucous membranes. Clinical features of PNH involve the gradual emergence of multiple yellow-brown papules and nodules, with histological examination demonstrating the presence of foamy tissue macrophages, spindle-shaped cells within a fibrocollagenous matrix, and Touton cells. We present a rare case of a 55-year-old female patient with progressively increasing facial nodules, where clinical, histopathological, and immunohistochemical findings clinched the diagnosis of PNH.