Background: Eosinophilic ulcer of the oral mucosa (EUOM), also known as traumatic eosinophilic granuloma or Rida-Fede disease, is an uncommon, benign and self-limited lesion of the oral mucous membrane. The tongue is the most common location of EUOM, accounting for up to 60% of the cases, with the lateral and dorsal surfaces being principally affected. EUOM clinically manifests as a painful, nodular inflammatory infiltration, usually with ulceration. Characteristic histological findings consist of dense subepithelial, mixed inflammatory infiltration with numerous eosinophils. The etiology of the disease is unknown.
Case Report: We present a case of a 9-year-old boy, in whom a painful ulceration, nonresponding to typical antiviral and antibacterial treatment, occurred on the lower lip. The histological study revealed intact epithelium without the unequivocal signs of cellular atypia and a dense infiltrate in the stroma mainly composed of eosinophils and histiocytes with CD30-negative cells. The histological diagnosis of EUOM was given. A rapid resolution of the lesion was observed following biopsy.
Conclusions: EUOM, a relatively rare and benign disease, infrequently presenting as a lesion on lips, may cause diagnostic difficulties to dermatologists as well as to dental surgeons and ENT specialists. Biopsy is recommended to rule out malignant etiology and avoid overtreatment.

Keywords: Lip - pathology, Follow-Up Studies, Eosinophilic Granuloma - pathology, Eosinophilia - pathology, Child, Antigens, CD30 - metabolism, Mouth Mucosa - pathology, Ulcer - pathology