Van der Woude syndrome is the most common single-gene disorder that causes cleft lip and palate, responsible for roughly 2% of all orofacial clefts worldwide. It affects somewhere between 1 in 35,000 and 1 in 100,000 newborns, depending on the population studied, and its hallmark feature is a pair of small pits or mounds on the lower lip that often appear alongside a cleft.1F1000Research. Case Report: Congenital absence of uvula and trismus – a rare presentation of Van der Woude syndrome Because the clefts it produces look nearly identical to the far more common non-syndromic clefts, it can be surprisingly easy to miss unless someone checks for those lip pits.
What Van der Woude Syndrome Looks Like
The three cardinal features are lower lip pits, cleft lip, and cleft palate, though not every affected person has all three. The lip pits are the most recognizable sign. They usually appear as small, symmetrical depressions on either side of the midline of the lower lip, sometimes accompanied by slight mounding of the surrounding tissue. In some people the pits are barely visible; in others they are deep enough to occasionally ooze a small amount of mucus. That secretion comes from underlying salivary gland tissue whose ducts empty directly into the pit.2PubMed. Congenital fistulae of the lower lip in Van der Woude syndrome: a histomorphological study The glands themselves are structurally similar to the minor salivary glands found elsewhere in the lip, with mostly mucous-producing units.3Journal of Applied Oral Science. Ultrastructural analysis of glands located in the wall of the congenital fistulae of the lower lip of patients with Van der Woude syndrome
Cleft lip and cleft palate occur in many affected individuals, and they can appear alone or together. Some people with Van der Woude syndrome have only the lip pits and no cleft at all, which is one reason the condition sometimes goes undiagnosed. Hypodontia, meaning one or more permanent teeth never develop, is another feature that shows up more often than you would expect by chance.4PubMed Central. Congenital lower lip pits: Van der Woude syndrome Rarer presentations have been reported too, including absent uvula and trismus (restricted jaw opening) in infants.5F1000Research. Case Report: Congenital absence of uvula and trismus – a rare presentation of Van der Woude syndrome
How It Is Inherited
Van der Woude syndrome follows an autosomal dominant pattern, which means a child needs to inherit only one copy of the mutated gene, from one parent, to be affected. The condition has high penetrance, estimated at 80% to 100%, so most people who carry the mutation will show at least some sign of it.6PubMed Central. Congenital lower lip pits: Van der Woude syndrome But penetrance and expressivity are different things. Even though the gene almost always does something, what it does varies enormously from one person to the next. One family member might have obvious bilateral lip pits and a complete cleft palate, while a sibling who carries the exact same mutation has only faint lip pits and nothing else. This variable expressivity is one of the syndrome’s most striking and most frustrating characteristics for families trying to understand what a diagnosis means for future children.
Each child of an affected parent has a 50% chance of inheriting the causative mutation. But predicting what that child’s symptoms will look like, even knowing the parent’s presentation, remains difficult. In genetic counseling, the key message is that carrying the mutation makes clefting and lip pits likely but says very little about severity.
The Genes Involved
The primary gene behind Van der Woude syndrome is IRF6, which encodes a protein called interferon regulatory factor 6. The gene sits on the long arm of chromosome 1. In 2002, researchers identified mutations in IRF6 by studying families with both Van der Woude syndrome and a related but more severe condition called popliteal pterygium syndrome, and they found that losing normal function of just one copy of IRF6 is enough to disrupt the way the face develops before birth.7PubMed Central. Mutations in IRF6 cause Van der Woude and popliteal pterygium syndromes Since then, dozens of different IRF6 mutations have been catalogued across families worldwide, including novel variants found in sub-Saharan African populations that had not been previously studied.8PubMed Central. Novel IRF6 mutations in families with Van Der Woude syndrome and popliteal pterygium syndrome from sub-Saharan Africa
IRF6 is not the whole story, though. A second gene, GRHL3, was identified in 2014 after researchers tracked down the cause in a large Finnish family and seven other families whose DNA showed no IRF6 mutation at all. GRHL3 mutations cause a nearly identical set of symptoms.9American Journal of Human Genetics. Dominant Mutations in GRHL3 Cause Van der Woude Syndrome and Disrupt Oral Periderm Development Although IRF6 mutations account for the majority of diagnosed cases, the discovery of GRHL3 matters for families who test negative for IRF6 changes and are wondering whether they truly have Van der Woude syndrome. Without checking both genes, some cases would be missed.
What Goes Wrong During Development
Both IRF6 and GRHL3 are involved in building a temporary protective layer of cells called the oral periderm, which lines the inside of the mouth during fetal development. The periderm acts as a kind of non-stick coating: it prevents the raw surfaces of developing tissues from fusing where they should not. When the periderm fails to form properly, tissue surfaces can stick together inappropriately, and the palatal shelves, which need to rise and fuse along the midline in a tightly controlled sequence, do not close the way they should. The result can be a cleft palate, a cleft lip, or both.
Research in mouse models has shown that embryos completely lacking Irf6 develop severe skin adhesions and orofacial clefts, while embryos lacking Grhl3 also lose their oral periderm and about one in six develop a cleft palate.10The American Journal of Human Genetics. Dominant Mutations in GRHL3 Cause Van der Woude Syndrome and Disrupt Oral Periderm Development Interestingly, the two genes appear to operate in separate but converging pathways rather than in a single chain. Disrupting both at once does not produce a worse outcome than disrupting either alone would predict, which suggests they contribute to periderm formation through different molecular routes that arrive at the same endpoint.11American Journal of Human Genetics. Dominant Mutations in GRHL3 Cause Van der Woude Syndrome and Disrupt Oral Periderm Development
An additional layer of complexity comes from a newer finding: one specific IRF6 mutation causes the IRF6 protein to shift from its normal location inside the cell nucleus to the cytoplasm, potentially disrupting its interaction with a signaling pathway involved in tissue growth and differentiation.12PubMed Central. A novel IRF6 gene mutation impacting the regulation of TGFβ2-AS1 in the TGFβ pathway: A mechanism in the development of Van der Woude syndrome This kind of mechanistic detail helps explain why different mutations in the same gene can sometimes produce different severity levels, though the picture is far from complete.
Why the Same Mutation Can Look So Different
The extreme variability in Van der Woude syndrome has puzzled researchers for decades. Two people in the same family can share the identical IRF6 mutation yet have strikingly different symptoms. One of the most dramatic examples is a pair of monozygotic (identical) twins who were discordant for the syndrome: one twin showed clear signs of Van der Woude, and the other did not, despite having the same DNA sequence.13PubMed Central. Mutations in IRF6 cause Van der Woude and popliteal pterygium syndromes
Epigenetics offers a partial explanation. Recent work comparing DNA methylation patterns, the chemical tags cells attach to DNA to dial gene activity up or down, has found differences in the regulatory regions around IRF6 and a related gene called TP63 that correlate with which type of cleft a person develops and how severe their symptoms are.14PubMed Central. DNA Methylation Effects on Van der Woude Syndrome Phenotypic Variability A separate study of monozygotic twins with Van der Woude syndrome found that differences in DNA methylation are a plausible mechanism for producing markedly distinct symptoms even when the underlying mutation is the same.15PubMed Central. DNA methylation differences in monozygotic twins with Van der Woude syndrome In other words, the genetic mutation loads the gun, but the epigenetic environment partly determines where it aims.
This has real implications for counseling. A parent with mild lip pits and no cleft can still have a child with a full cleft lip and palate, and vice versa. There is currently no clinical test that predicts severity from the mutation alone.
The Connection to Popliteal Pterygium Syndrome
Van der Woude syndrome shares a genetic cause with a rarer and more severe condition called popliteal pterygium syndrome. Both are caused by mutations in IRF6, and they share core features like lip pits and orofacial clefts. But popliteal pterygium syndrome also involves skin webbing behind the knees (popliteal pterygia), fused fingers or toes, skeletal abnormalities, and genital anomalies.16PubMed Central. A Complex Intrachromosomal Rearrangement Disrupting IRF6 in a Family with Popliteal Pterygium and Van der Woude Syndromes
The two conditions were once thought to be points on a single spectrum, but the pattern of IRF6 mutations tells a more nuanced story. Analysis of over 300 families has shown that Van der Woude mutations tend to cause a simple loss of function in one copy of the gene, while popliteal pterygium mutations are more likely to produce a protein that actively interferes with the remaining normal copy, a so-called dominant-negative effect.17PubMed Central. Prevalence and nonrandom distribution of exonic mutations in interferon regulatory factor 6 in 307 families with Van der Woude syndrome and 37 families with popliteal pterygium syndrome Both conditions can even appear in the same family, which complicates genetic counseling further.
Dental Problems Beyond the Cleft
People with Van der Woude syndrome face dental challenges that go beyond whatever cleft repair they may have needed. Hypodontia, the congenital absence of one or more permanent teeth, occurs in more than a third of individuals with the syndrome, roughly double the rate seen in people with non-syndromic cleft palate and several times the rate in the general population. The teeth most often missing are the permanent second premolars and the upper lateral incisors.18European Journal of Orthodontics. Dental age, agenesis, and morphological anomalies in individuals with Van der Woude syndrome and isolated cleft palate Missing teeth affect bite alignment, jaw growth, and the long-term plan for orthodontic treatment, so dental monitoring from an early age is especially important for children with this diagnosis.
Speech Outcomes and Midfacial Growth
One question parents often ask after a cleft repair is whether speech will develop normally. For children with Van der Woude syndrome, the answer tends to be more guarded than for children with non-syndromic clefts. In one study, all children with the syndrome who were still being followed at age ten were still receiving speech therapy, compared with just over half of children with non-syndromic clefts.19PubMed Central. Surgical, Speech, and Audiologic Outcomes in Patients with Orofacial Cleft and Van der Woude Syndrome The need for a secondary surgery to correct velopharyngeal dysfunction, the inability of the soft palate to fully close off the nose during speech, was also higher in the Van der Woude group, though the difference did not reach statistical significance in that particular study.
Midfacial growth is another area of concern. A separate analysis found that more than four in ten children with Van der Woude or popliteal pterygium syndrome who were five years or older had midfacial retrusion, a setback of the middle portion of the face, at a rate significantly higher than in non-syndromic cleft patients. The rate of palatal fistula, a small opening that can persist or recur after palate repair, was also markedly elevated.20PubMed. Anatomic Severity, Midfacial Growth, and Speech Outcomes in Van der Woude/Popliteal Pterygium Syndromes Compared to Nonsyndromic Cleft Lip/Palate These findings suggest that the underlying tissue biology in Van der Woude syndrome may make surgical repair somewhat less predictable, and clinicians who manage these children should be prepared for a longer and more involved treatment course.
Surgical Treatment of Lip Pits
Lip pits may seem like a minor cosmetic issue compared with a cleft, but they can bother people enough to seek surgery. The pits sometimes produce visible mucus, can become infected, and are a noticeable marker of the syndrome. Removing them surgically sounds straightforward, but the anatomy is variable enough that no single technique works well for everyone. Each pit can differ in size, depth, and location, and bilateral pits pose the additional question of whether to remove both through separate vertical cuts or a single horizontal incision that bridges both.21PubMed Central. Surgical Treatment of Lip Pits in Van der Woude Syndrome: A Preliminary Retrospective Study of 24 Patients
A systematic review of surgical techniques found that simple excision, the most basic approach, carries a higher risk of complications like mucocele formation (a cyst that develops when salivary gland tissue is not fully removed) and recurrence of the pit itself. More involved techniques, including vertical wedge excision, an inverted-T lip reduction, and a method called the Mutaf-Goldstein technique, tend to produce better aesthetic results with fewer complications.22PubMed. Treatment of lower lip pits in Van der Woude syndrome: a systematic review For large or deep pits, the main surgical challenge is that removing all of the pit tissue can leave a substantial defect in the lip, leading to shortening or bulbous widening from scarring.23PubMed Central. Surgical Treatment of Lip Pits in Van der Woude Syndrome: A Preliminary Retrospective Study of 24 Patients Timing the pit excision relative to any cleft surgery requires coordination with the broader surgical plan.
Diagnosis and When It Gets Missed
The diagnosis of Van der Woude syndrome is usually clinical. If a baby is born with a cleft and has visible lip pits, an experienced clinician will recognize the combination. The trouble comes when the lip pits are subtle or absent, or when the cleft occurs without other features. In those cases the condition can easily be classified as an ordinary non-syndromic cleft, which matters because the recurrence risk for future children is different. For a non-syndromic cleft, the recurrence risk to siblings is generally low, in the range of 2% to 5%. For Van der Woude syndrome, the risk to each child of an affected parent is 50%, because of the autosomal dominant inheritance.
Genetic testing for IRF6 and GRHL3 mutations can confirm the diagnosis. Prenatal detection is also possible; one early case report described diagnosing a cleft lip at 11 weeks of gestation by embryoscopy in a family known to carry the syndrome.24PubMed. Prenatal diagnosis of cleft lip at 11 menstrual weeks using embryoscopy in the van der Woude syndrome Today, families with a confirmed mutation can use standard prenatal genetic testing or preimplantation genetic diagnosis if they want to know before or during pregnancy whether a child is affected. The value of screening extends beyond a single family, too: identifying Van der Woude syndrome in populations that have historically been underrepresented in genetic studies, as recent work in Nigerian and Ethiopian families has shown, ensures that counseling and prenatal options are available more broadly.25PubMed Central. Novel IRF6 mutations in families with Van Der Woude syndrome and popliteal pterygium syndrome from sub-Saharan Africa
Lessons from Animal Models
Mouse and zebrafish experiments continue to refine the understanding of how IRF6 and GRHL3 drive facial development, and some of the findings have been genuinely surprising. In one line of research, scientists attempted to rescue mice that completely lacked Irf6 by reintroducing the gene only in the basal layer of the skin. The rescue worked for many parts of the body: adhesions between the limbs and trunk resolved, and the mice survived past birth, which knockout mice normally do not. But orofacial clefts and adhesions between the palate and tongue persisted, and the esophagus remained stuck shut.26PubMed Central. IRF6 expression in basal epithelium partially rescues Irf6 knockout mice The implication is that IRF6 needs to be active in the periderm itself, not just in the cells underneath, to prevent oral clefting. That finding underscores how tightly the syndrome’s pathology is linked to periderm biology, a tissue layer that is temporary and often overlooked.
Zebrafish have contributed as well. The GRHL3 mutations found in human families were tested in a zebrafish model and shown to knock out periderm development, consistent with a dominant-negative mechanism rather than simple loss of function.27The American Journal of Human Genetics. Dominant Mutations in GRHL3 Cause Van der Woude Syndrome and Disrupt Oral Periderm Development The difference matters because the way a mutation breaks a gene, whether it silences one copy or produces a toxic version of the protein, influences how severe the disease is and potentially how it might be treated. For now, there is no gene therapy for Van der Woude syndrome, but these models provide the groundwork for understanding where an intervention would need to act.