White sponge nevus (WSN) is a rare genetic disease with AD inheritance that is mostly diagnosed in oral and dental medical departments as the most obvious clinical sign is the dyskeratotic hyperplasia in form of white spongy plaques in the oral mucosa. According to published data from Hungary, 13 patients were diagnosed with white sponge nevus at the Departments of Oral Medicine and Conservative Dentistry of the Semmelweis University, with histology and detailed ultrastructural examination of the mucosal lesions. Searching the literature, we have not found publications with genetic only ultrastructural data of Hungarian white sponge nevus patients. Here we present a father and his daughter diagnosed with white sponge nevus in our Department. The 42-year old father already underwent several shave biopsies and electro-cauterization with the diagnosis of oral leukoplakia. His 17-year old daughter had not only diffuse oral, but also genital mucosa involvement. The genetic analysis showed a known pathogenic variant in the KRT4 gene (KRT4 c.438-440delCAA; a variant identified first in two Scottish patients) in both patients. Currently, we are investigating other variants in the KRT4 gene, as this gene is known to carry more INDEL and/or SNP variations compared with the average for the same chromosome. So far, an unknown novel KRT4 INDEL variant (a 42-nucleotide long insertion) has been identified in both patients. We are studying the potential involvement of this INDEL variant in the pathology of the disease as a disease modifier.

ESDR313 - A case of familiar white sponge nevus with KRT4 gene variants

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