Understanding Prader-Willi syndrome

Prader-Willi Syndrome (PWS) is a rare and complex neurodevelopmental genetic disorder with multisystem manifestations. It is identified as the most prevalent genetic cause of life-threatening obesity in humans. PWS results from errors in genomic imprinting, typically involving the lack of expression of genes within the 15q11-q13 region of chromosome 15, inherited from the father. These abnormalities are often due to either a paternal deletion (60%) or maternal disomy 15 (35%), where both copies of chromosome 15 are inherited from the mother. The disorder is also attributed to defects within an imprinting centre (microdeletion or epimutation) in the chromosome region. The occurrence of PWS is estimated to be approximately 1 in 15,000 individuals.¹

Clinical course development and presentation in Prader-Willi syndrome

The clinical course of PWS is divided into two stages:

1. Failure to thrive as the first stage
2. Hyperphagia leading to obesity as the second stage

Recent research indicates a more gradual and complicated progression with the emergence of nutritional phases.

The five main nutritional phases of PWS are listed below:

• Phase 0 - Begins in the uterus with decreased foetal movement and growth restriction
• Phase 1 - From birth to 15 months characterised by hypotonia in non-obese infants
  • Subphase 1a: Feeding difficulties with or without failure to thrive
  • Subphase 1b: Steady infant growth and weight gain 
• Phase 2 - starts around age 2, marked by weight gain
  • Subphase 2a: Weight gain without a change in appetite
  • Subphase 2b: Weight increases with increased interest in food
• Phase 3 - Around age 8 with hyperphagia and a lack of fullness after eating, leading to food-seeking behaviours
• Phase 4 - Insatiable appetite diminishes¹

Dental issues associated with Prader-Willi syndrome

Individuals with PWS are at an elevated risk of developing several oral diseases due to dietary challenges. Enamel hypoplasia is associated with malnutrition and low birth weight and is prevalent in the initial phase of PWS. Reduced salivary quantity and quality are due to salivary gland atrophy. This in turn is linked to low birth weight. The saliva in PWS patients has increased levels of salivary ions and proteins (mucin-7). Hence it tends to be more viscous, sticky, and sparse. It is less effective in performing its functions, like remineralising enamel effectively.^2,3 

Inadequate salivary secretion may also increase susceptibility to dry mouth, oral infections, mucosal lesions, and plaque accumulation. Delayed tooth eruption and candidiasis are also common in these individuals.^2,3 There is tooth wear from attrition, erosion, or abrasion. Toothwear can also influence the jaw bones and facial features.⁵

Poor oral hygiene in addition to reduced salivary flow heightens the risk of dental caries (tooth decay). The presence of hyperphagia further worsens this, causing increased consumption of soft carbohydrates. Early childhood caries are a significant risk even in the first year of life. Dental malocclusion, occlusal trauma, and inadequate plaque control lead to periodontal issues.² A triangular mouth with downturned commissures and a thin upper lip has been noted in individuals with PWS.² They also commonly have angular cheilitis, dentoalveolar abscess, hypotonic tongue, mouth breathing, and root stumps.³

Poor speech development is common in children with PWS.^3,4 Hypotonia negatively impacts speech articulation, rate, and quality due to reduced oral motor skills. Other normal oral functions like sucking, chewing, and swallowing are affected.³

Importance of dental care for individuals with Prader-Willi syndrome

Early diagnosis, adherence to preventive guidelines, and a multidisciplinary approach are crucial for improving the quality of life in PWS patients. The ability of PWS patients to cooperate should be assessed to provide effective dental care for them and maintain optimal oral hygiene. Paediatric dentists play a vital role in managing oral health for children with PWS. They can coordinate appointments with different dental specialists on the same day. This minimises the burden of multiple hospital visits and non-cooperation with patients. Treatment protocols should be established collaboratively by all the specialists to provide comprehensive care for PWS patients.²

Regular paediatric dental appointments and preventive measures like topical fluoride application, and teeth cleaning (every 3-4 months) should be implemented. Prosthodontic rehabilitation must be considered in young adults with PWS to address dental abrasion and wear. Patients able to cooperate may undergo dental procedures that can be performed under local anaesthesia. However, the use of mouth openers is suggested due to poor muscle control. Visual aids like drawings and posters may aid in oral health education.²

Tips for parents and caregivers of children with Prader-Willi syndrome

Dental care for children with PWS requires special attention to ensure optimal oral hygiene and overall health. A structured dental care routine should be established at an early age (when the child’s first tooth emerges) and followed diligently. The child should be assisted by a parent with brushing of teeth, using appropriate toothpaste as recommended by the dentist. The consumption of sugary snacks and drinks should be limited. A dentist experienced in treating children with special needs, including PWS, should be approached by the parents for dental care. The child’s condition and specific dental concerns should be communicated with the dentist and appropriate care should be sought. 

Summary

Prader-Willi Syndrome (PWS) is a complex genetic disorder that affects various aspects of an individual's health, including oral health. Individuals with PWS experience a range of dental issues including delayed tooth eruption, malocclusion, bruxism, and increased risk of dental caries. These issues can be attributed to underlying factors such as hypotonia, hyperphagia, and changes in the composition of saliva. Dental problems may also contribute to difficulties in chewing, swallowing, and speech articulation affecting the quality of life. Individuals with PWS require a multidisciplinary approach involving different dental specialists, therapists, and caregivers. Periodic dental checkups, early assessments, preventive dental care measures, and orthodontic and prosthodontic interventions are essential to treat dental issues in these patients. Establishing a consistent dental care routine, and encouraging good oral hygiene habits are essential in ensuring optimal dental health outcomes for children with PWS.