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KRT4 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

KRT4 gene

The KRT4 gene provides instructions for making keratin 4, a protein that provides structural support to the moist linings of the body.

Normal Function

The KRT4 gene provides instructions for making a protein called keratin 4. Keratins are a group of tough, fibrous proteins that form the structural framework of epithelial cells, which are cells that line the surfaces and cavities of the body. Keratin 4 is found in the moist lining (mucosae) of the mouth, nose, esophagus, genitals, and anus.

Keratin 4 partners with a similar protein, keratin 13 (produced from the KRT13 gene), to form molecules known as intermediate filaments. These filaments assemble into strong networks that provide strength and resilience to the different mucosae. Networks of intermediate filaments protect the mucosae from being damaged by friction or other everyday physical stresses.

Health Conditions Related to Genetic Changes

White sponge nevus

At least six mutations in the KRT4 gene have been found to cause white sponge nevus, a condition that results in the formation of white patches of tissue called nevi that appear as thickened, velvety, sponge-like tissue. These nevi most often occur on the mouth (oral) mucosa. Rarely, white sponge nevus occurs on the mucosae of the nose, esophagus, genitals, or anus.

The KRT4 gene mutations that cause white sponge nevus disrupt the structure of keratin 4. As a result, keratin 4 does not fit together properly with keratin 13, leading to the formation of irregular intermediate filaments that are easily damaged with little friction or trauma. Fragile intermediate filaments in the oral mucosa might be damaged when eating or brushing one's teeth. Damage to intermediate filaments leads to inflammation and promotes the abnormal growth and division (proliferation) of epithelial cells, causing the mucosae to thicken and resulting in white sponge nevus.

Other Names for This Gene

  • CK-4
  • CK4
  • CYK4
  • cytokeratin 4
  • K4
  • keratin 4, type II
  • keratin, type II cytoskeletal 4
  • type-II keratin Kb4

Frequently Asked Questions

definitive diagnosis is made by sequencing the KRT4 gene from a blood or saliva sample. Targeted next‑generation sequencing panels for mucosal disorders or whole‑exome sequencing can identify pathogenic variants. The test result will indicate whether the mutation is likely disease‑causing and can guide family counseling.
White sponge nevus typically presents as thick, white, velvety patches on the inside of the lips, cheeks, or tongue. The lesions are usually painless but can become inflamed or sore after eating, brushing, or chewing. Parents should look for these patches, especially if they appear early in childhood or are present in multiple oral sites.
Good oral hygiene with a soft‑bristled toothbrush and mild, non‑irritating mouth rinses can help. If inflammation occurs, a topical steroid rinse or a short course of oral steroids may be prescribed by a dentist or dermatologist. Avoiding spicy, acidic, or hot foods that irritate the lesions also reduces discomfort.
Yes, although the mouth is most commonly involved, white sponge nevus can also appear on the nasal lining, esophagus, genitals, or anus. Patients should report any new white patches or soreness in these areas to a clinician, as early recognition can prevent secondary infections or complications.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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