The main features include
- hypotonia (floppiness)
- a distinctive appearance, with a high, rounded forehead, widely spaced eyes and a large mouth with a thin upper vermillion (lip)
- streaks or patches of darker (hyperpigmentation) or lighter (hypopigmentation) skin
- developmental delay (see entry Global Developmental Delay); varies from mild to severe
- learning difficulties (see entry Learning Disability)
- sparse hair or bald patches around the temples, and sparse eyebrows.
A number of other features may be associated with PKS, including heart defects, gastro-oesophageal reflux, umbilical hernia, missing teeth and hearing and vision problems. Diaphragmatic hernia occurs when there is a hole in the muscle that separates the contents of the abdomen from the chest, so part of the gut may develop in the chest, leaving too little room for the lungs to grow. This occurs more frequently in babies with PKS.