A non-familial case of white sponge naevus: Diagnostic and clinical implications

Dear Editor,

White sponge naevus (WSN) is a rare, benign genetic disorder affecting oral keratinisation, most commonly inherited in an autosomal dominant pattern. We present a sporadic case in a 29-year-old male with no family history, who exhibited asymptomatic, bilateral white spongy plaques on the buccal and labial mucosa. The current case aims to disseminate knowledge regarding the diagnostic challenge of sporadic WSN. Importantly, it highlights the clinical acumen required to differentiate it from common plaque-like lesions occurring in the oral mucosa. This will enable the clinician to provide appropriate management and avoid unnecessary treatment.

A 29-year-old man presented with a 15-year history of persistent white, raised lesions on his buccal mucosa and mucosal aspect of the lower lips. He had consulted multiple dentists and dermatologists and tried various treatments, including topical retinoids, systemic fluconazole, prebiotics, multivitamins, and different mouthwashes, but none provided lasting relief. He denied any relevant medical history or habits such as lip licking or cheek biting. There was no family history of similar lesions.

Intraoral examination revealed partially scrapable, thick, shaggy white plaques with a frayed surface, along the occlusion line of bilateral buccal mucosa and extending inferiorly [Figure 1], as well as on both upper and lower labial mucosa.

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Figure 1:

Diffuse, partially adherent, thick, shaggy white plaques with a frayed surface on the right buccal mucosa.

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The differential diagnosis included morsicatio buccarum, oral candidiasis, oral lichen planus, sporadic WSN, and Darier’s disease. Based on the clinical features, a provisional diagnosis of hypertrophic oral lichen planus was made. Since the patient had recently used topical and systemic antifungal agents without improvement, topical clobetasol propionate was prescribed to be applied three times daily for 1 week.

Following treatment, the patient reported complete resolution of the lesions [Figure 2], prompting a tapering of the steroid to twice daily. However, the lesions recurred within a week. The same treatment was continued, and a custom splint was advised to minimise possible unconscious or nocturnal cheek biting. There is no established role for steroids in the treatment of WSN. Any initial response to steroid therapy may be due to the resolution of a superimposed inflammatory component rather than a direct effect on the primary lesion.

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Figure 2:

Complete resolution of the lesion on the right buccal mucosa with potent topical stroid application.

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Despite continued use of topical steroids and the protective occlusal splint, the lesions persisted. Histopathological analysis showed hyperplastic, hyperparakeratinised stratified squamous epithelium covering a moderately collagenous connective tissue stroma. The epithelium showed marked acanthosis and intracellular oedema within the spinous layer, along with vacuolated cells in the basal layer. The connective tissue exhibited mild chronic inflammatory infiltrate and moderate vascularity. [Figure 3]. These findings were consistent with WSN. As WSN is benign and has no definitive treatment, the patient was educated about the diagnosis, reassured of its non-progressive nature, and placed under regular follow-up.

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Figure 3:

Photomicrograph showing hyperplastic, hyperparakeratinised stratified squamous epithelium overlying a moderately collagenous connective tissue stroma. The epithelium exhibited acanthosis and intracellular edema in numerous cells within the spinous layer. Vacuolated cells were also observed in areas of the basal cell layer. (Haematoxylin and eosin, 100x)

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Initially described by Hyde in 1909, the term “white sponge naevus” was introduced by Canon in 1935. This autosomal dominant genodermatosis is estimated to affect fewer than 1 in 2,00,000 people worldwide and occurs without preference for race or gender.¹ In this case, the patient noted the onset of lesions at age 13, consistent with common presentation timing. Although WSN is usually hereditary, no family history was reported, suggesting a sporadic form likely due to a de novo mutation.²

WSN arises from mutations in the keratin 4 (KRT4) or keratin 13 (KRT13) genes, which encode mucosa-specific intermediate filament proteins essential for epithelial integrity.³ While these mutations are commonly found in familial cases, Liu et al. found that only one in five sporadic cases exhibited keratin gene mutations, suggesting additional genetic or epigenetic mechanisms may be involved.²

Clinically, WSN typically presents as bilateral, symmetrical, thickened, spongy white plaques, most commonly on the buccal mucosa but occasionally involving other mucosal sites, such as the labial mucosa, floor of the mouth, nasal, or genital mucosa.⁴ The presentation can range from subtle, asymptomatic patches to extensive lesions causing cosmetic or functional concern, as seen in our patient.

The differential diagnosis includes both hereditary and acquired white oral lesions. Paediatric differentials include leukoedema, dyskeratosis congenita, hereditary benign intraepithelial dyskeratosis, and Darier’s disease. Acquired conditions such as oral candidiasis, focal epithelial hyperplasia, HPV-associated florid papillomatosis, and oral lichen planus may mimic WSN.⁵ In this case, candidiasis was excluded based on antifungal response, and lichen planus was initially suspected but ruled out following biopsy.

Histopathologically, white sponge naevus (WSN) shows acanthosis, hyperparakeratosis, and vacuolated keratinocytes with a “fried egg” appearance. In our case, the lesion demonstrated marked acanthosis, hyperparakeratinized stratified squamous epithelium, and vacuolated basal cells, consistent with the epithelial features of WSN. Intracellular edema within the spinous layer and vacuolated basal keratinocytes further support the presence of abnormal keratinocyte differentiation. Although perinuclear eosinophilic condensation and Odland bodies were not specifically observed, the combination of acanthosis, hyperparakeratosis, and vacuolated keratinocytes in the suprabasal and basal layers aligns with the histopathological profile of WSN. The underlying connective tissue showed mild chronic inflammatory infiltrate and moderate vascularity, which is occasionally noted in WSN but is not a defining feature. Taken together, these findings justify the diagnosis of white sponge naevus in correlation with the clinical presentation.

Malignant transformation in WSN is exceedingly rare, with only a single case reported by Downham and Plezia, potentially linked to long-term immunosuppression with prednisone.⁶ Several therapies, such as antibiotics, β-carotene, antihistamines, topical retinoic acid, and even surgical or laser approaches, have been attempted with inconsistent results.⁷

Proper identification of such sporadic cases of WSN without a family history is essential. This underscores the importance of distinguishing WSN from premalignant and infectious oral conditions to avoid misdiagnosis and unnecessary treatment.