Benign fibrous histiocytoma occurred in the alveolar mucosa accompanying with sialidosis type 2 in Japanese infant

Benign fibrous histiocytoma with sialidosis which is a rare metabolic disorder resulting from the deficiency of a lysosomal enzyme, and α-neuraminidase, as one of lysosomal storage diseases. The patient; male infant (2 years and 8 months), with infantile form of sialidosis type 2, shows extensive gingival enlargement and gingival tumor with a painless mass (4 × 2 × 2 cm), which grew gradually on the gingiva of left maxillary deciduous molar region. A tumorectomy was performed to improve the mastication. The surgical specimen had many histiocytes positive for CD68 with cytoplasmic vacuoles, which is a specific feature in the patient of glycoprotein degradation disorder. These histiocytes were also positive for lysozyme. The gingival tumor was diagnosed as benign fibrous histiocytoma. The present report is discussed glycoprotein degradation disorder accompanying with gingival hyperplasia.