Diffuse dermal mucinosis secondary to colony-stimulating factor 1 receptor monoclonal antibody treatment: A novel and peculiar drug-induced diffuse cutaneous mucinosis

Abstract

Colony-stimulating factor 1 receptor (CSF1R) inhibitors represent a new class of immune-modulatory drugs, mostly investigated in clinical trials in different malignant neoplasms. Four patients, diagnosed with recurrent or advanced malignant neoplasm and treated with a combination of anti-programmed death ligand 1 and anti-CSF1R

monoclonal antibodies, developed an asymptomatic cutaneous eruption characterized by an ill-defined pseu- doedematous to waxy diffuse infiltration with a reticular cobblestone-like pattern. Histopathological examination

revealed diffuse mucin deposition involving the superficial and mid-dermis with fragmented and scattered elastic fibers. The exact pathogenic mechanisms implicated in the development of mucin deposits in patients treated

with CSF1R inhibitors remain to be elucidated. A reduced degradation and clearance of components of the extra- cellular matrix by macrophages secondary to CSF1 pathway inhibition may be hypothesized. Shredding and frag- mentation of elastic fibers may be a result of the increased accumulation of mucopolysaccharides. This

observation illustrates the new spectrum of skin-related toxicities secondary to new targeting therapies. This may contribute to a better understanding of the underlying pathogenic mechanisms in skin diseases characterized by a persistent dermal glycosaminoglycan deposition.