Based on my analysis, the image and the Harrison's table give a clear picture. Let me also check what that table said about white sponge nevus specifically.
The image in your photo shows whitish, thickened, irregular plaques on the inner lower lip (labial mucosa) that feel rubbery/spongy — and you say it's not painful. The most likely diagnoses, from most to least likely, are:
Most Likely: Leukoedema or White Sponge Nevus (Hereditary Mucosal Leukokeratosis)
Looking at your photo, the key features are:
- Diffuse whitish-gray, thickened, corrugated plaques on the inner lip mucosa
- Rubbery / spongy texture (you said "like rubber")
- No pain
- Bilateral appearance
This matches a condition called White Sponge Nevus (WSN) — a benign, hereditary condition caused by mutations in keratin genes (KRT4 or KRT13). The oral epithelium thickens and takes on a spongy, rubbery, wrinkled texture.
Comparison with a clinical reference image of White Sponge Nevus:
The resemblance to your photo is strong — note panel (c) which shows the inner upper lip with identical-looking whitish, spongy, thickened mucosa.
Other Possibilities to Consider
| Condition | Why it fits | Why it might not |
|---|
| Leukoedema | Diffuse, gray-white, folded mucosa; very common; benign | Usually disappears when stretched |
| Oral leukoplakia | White plaque that can't be wiped off | Usually has sharper borders; associated with tobacco/alcohol |
| Frictional keratosis | Thickened white area from chronic irritation | Usually more localized |
| Oral candidiasis (thrush) | White patches in mouth | These would scrape off with a tongue blade — rubbery patches that stay are NOT candida |
According to Harrison's Principles of Internal Medicine (2025): White sponge nevus is described as a "painless, whitish thickening of epithelium; adolescence/early adulthood onset; familial" — located on the oral mucosa and vagina, and is benign and permanent.
What You Should Do
- See a dentist or oral medicine specialist — this needs an in-person examination
- The doctor may do a biopsy to confirm the diagnosis, especially to rule out dysplasia or early leukoplakia
- Ask family members if they have similar patches inside their mouth (WSN is hereditary — autosomal dominant)
- Avoid tobacco, alcohol, and betel nut — these can cause similar-looking but more dangerous lesions (true leukoplakia, which carries cancer risk)
⚠️ Important: While this likely looks benign (especially if it has been present for years and runs in your family), any persistent white patch in the mouth that cannot be explained should be evaluated by a professional. A biopsy is the only way to definitively rule out dysplasia or malignancy.