Clinicopathological characteristics of xeroderma pigmentosum associated with keratoacanthoma: a case report and literature review.

OBJECTIVE To investigate the clinicopathological characteristics, diagnosis and differential diagnosis, and treatment of xeroderma pigmentosum associated with keratoacanthoma in an infant. METHODS The clinical manifestations of xeroderma pigmentosum associated with keratoacanthoma were assessed in an 18-month old boy. The morphological and histological features of the lesions were examined by light microscopy. RESULTS An 18-month old boy was admitted with unequal size, irregularly shaped brown spots, patches and depigmentation spots on his face. A well-circumscribed hemispherical mass measuring 3 cm × 3 cm with smooth surface and brown patches was observed beneath his left lower eyelid. Light microscopic examination of the skin lesions revealed epidermal hyperkeratosis, chronic inflammatory infiltration of the superficial dermal layer, and increases in melanocytes and melanin in the basal layer. Scanning microscopy showed that the mass beneath the left lower eyelid was cup-shaped, consisting of proliferating squamous cells with a central keratin plug. The squamous epithelium was acanthotic with hypergranulosis. The adjacent epidermis formed exophytic projections resulting in a silhouette likened to lips. An associated inflammatory reaction was observed within the stroma surrounding the mass. The patient was treated with a combination of antioxidant drugs, keeping the child from light and surgical excision of the mass. No recurrence has been observed. CONCLUSIONS Xeroderma pigmentosum of infancy is a rare disease, and association with keratoacanthoma is even rarer. This condition should be considered in the differential diagnosis of freckles, Rothmund-Thomson syndrome and porphyria.