Isolated Benign Primary Cutaneous Plasmacytosis in Children: Two Illustrative Cases

Background Plasma cells are normally found in bone marrow and the intestinal tract. They appear in the skin in malignant conditions, autoimmune diseases, infection, and idiopathic and poorly understood disorders such as primary nodular amyloidosis. It is uncommon to find collections of plasma cells in the skin in the absence of these conditions. Observations We present 2 cases of cutaneous plasmacytosis, one in a white, female adolescent aged 15 years with an 11-year history of a solitary, asymptomatic, violaceous plaque on the left anterior tibia and the other in a white, male child aged 7 years with a 2-year history of a solitary erythematous plaque on the right anterior tibia. In both patients, infiltration of mature polyclonal plasma cells was confined to an area on the skin with papulonodules. There was no history of previous trauma, malignant conditions, autoimmune disease, or infection in either child. Conclusion Although incipient or occult systemic disease cannot be definitively ruled out, the course of these 2 individuals suggests that isolated primary cutaneous plasmacytosis in children is a benign chronic process with no adverse sequelae.