Reticulohistiocytoma (RH) is a dermal histiocytic infiltration composed of large histiocytes with eosinophilic glassy cytoplasm. RH is classified into three clinical forms: solitary RH, diffuse cutaneous RH without systemic involvement and multicentric reticulohistiocytosis with systemic diseases. Solitary RH generally manifests as a nodular lesion in adults without accompanying systemic diseases. Herein, we describe a case of solitary RH with an atypical clinical manifestation as a red-brown-colored plaque in a 2-year-old boy. Atypical presentations of RH may pose diagnostic difficulty unless RH is considered. A correct diagnosis of RH can ensure avoidance of unnecessary invasive procedures.