Abstract

A 19-month-old girl presented with nodular rash for one year, which began as isolated lesions on her extremities and gradually progressed to involve her face and torso. Evaluation for autoimmune (lupus panel) and infectious etiologies (fungus, bacteria, mycobacteria) were negative. Punch biopsies showed diffuse deep dermal proliferation of spindled cells interspersed with keloidal-like collagen. The epidermis was uninvolved. The lesional cells were spindled, plump, with amphophilic to foamy cytoplasm. Rare touton giant cell was noted. Immunohistochemical staining showed strong and diffuse CD68 and CD163 positivity but negative for CD1a, CD207, ALK D5F3, S100 protein, and BRAF V600E (VE1). A diagnosis of non-Langerhans cell histiocytosis was established. Further laboratory and imaging studies ruled out systemic involvement of the disease. A comprehensive molecular study identified mutations in ANKRD26 and PDGFRB genes. Cutaneous non-Langerhans cell histiocytosis (non-LCH) is a rare and biologically benign entity with variable clinical outcomes. Non-LCH cutaneous histiocytoses can be broadly classified into (1) xanthogranuloma family which encompasses a spectrum of diseases with overlapping histologic and clinical features, and (2) non-xanthogranuloma family. Xanthogranuloma family of non-LCH is characterized by a proliferation of histiocytes with both macrophage and dendritic cell differentiation, negative BRAF mutation, and rare Touton-type giant cells. Etiology is unknown and the clinical manifestations appear to depend on the maturational state of the constituent cells. Most lesions resolve spontaneously, while disseminated and mature forms persist longer. Albeit unknown significance, ANKRD26 and PDGFRB gene mutation in cutaneous non-LCH was not previously described in the literature.

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