Genetics and Epidemiology - Van der Woude syndrome is inherited as an autosomal dominant disease caused by a mutation in a single gene. - The disease has high penetrance at about 96%. - Phenotypic expression varies from lower lip pits with cleft lip and cleft palate to no visible abnormalities. - Approximately 88% of VWS patients display lower lip pits. - VWS is the most common orofacial clefting syndrome, accounting for 2% of CLP cases. - Prevalence of VWS is 1 in 35,000 to 1 in 100,000 births. - Equal occurrence in males and females. - Higher prevalence in certain populations (e.g., Native Americans, Finnish).

Pathophysiology - Lip pits occur during embryogenesis due to IRF6 mutations. - Cleft lip and cleft palate develop during embryonic development. - There are three types of lip pits: midline upper, comissural, and lower lip. - Lip pits extend into the orbicularis oris muscle, ending in blind sacs surrounded by mucous glands. - Mucous is sometimes excreted when the muscles contract.

Diagnosis and Differential Diagnosis - Clinical diagnosis is based on orofacial clefts and lip pits. - Submucous cleft palate may not be detected except through finger palpation. - Approximately 15% of VWS cases with orofacial clefts, without prominent lip pits, cannot be easily distinguished from non-syndromic forms of orofacial clefting. - Dentists may detect hypodontia commonly associated with VWS. - VWS clinical signs are similar to those of popliteal pterygium syndrome (PPS). - Differential diagnosis includes popliteal pterygium syndrome, orofacial digital syndrome, Stickler syndrome, Pierre Robin sequence, and Robinow syndrome.

Genetic Counseling and Treatment - Genetic counseling involves discussing disease transmission in an autosomal dominant manner. - Parents have a 50% chance of passing on their mutated IRF6 allele to their child. - Cleft patients with lip pits have a ten times greater risk of having a child with cleft lip with or without cleft palate. - Different types of clefts may occur horizontally and vertically within the same pedigree. - A complete family history is important to ensure the patient does not have non-syndromic clefting. - Autosomal dominant inheritance pattern. - Genetic testing (e.g., mutation screening of IRF6 gene). - Prenatal diagnosis options (e.g., ultrasound, DNA analysis). - Multidisciplinary approach to treatment (e.g., surgery, orthodontics, speech therapy). - Psychological support for affected individuals and families.

Cardinal Signs, Associated Features, and Treatment - Cardinal signs of Van der Woude syndrome include cleft lip and/or cleft palate, lip pits, hypodontia, fistulas, and abnormal frenulum. - Associated features may include hearing loss, syndactyly, hypoplasia of the nasal alae, ankyloglossia, and delayed speech development. - Lip pits may be surgically removed for aesthetic reasons or discomfort due to inflammation or chronic saliva excretion. - Spontaneous shrinkage of lip pits has occurred in rare cases. - Chronic inflammation can cause squamous-cell carcinoma. - Complete removal of the lip pit canal is essential to prevent mucoid cysts. - Other associated conditions are treated as they would be if they were non-syndromic.