Consensus recommendations on lymphedema in Phelan-McDermid syndrome.

Phelan-McDermid syndrome (PMS) is a neurodevelopmental disorder caused by deletions 22q13.3 or pathogenic variants in the SHANK3 gene. Lymphedema can be a clinical feature in 10-25% of individuals with PMS due to a deletion 22q13.3, but is not observed in those with a SHANK3 variant. This paper forms a part of the European consensus guideline for PMS and focuses on what is known regarding lymphedema in PMS in order to present clinical recommendations. The mechanism causing lymphedema in PMS is unknown. Lymphedema can be suggested by pitting oedema of the extremities or, in later stages, non-pitting swelling. It can occur already at a young age and be progressive if untreated, impacting daily functioning. Lymphedema can be treated using existing general multidisciplinary management guidelines, taking the functioning of the individual with PMS into account. Furthermore, well-known risk factors for the development of lymphedema as lack of physical activities and weight gain/obesity should be addressed. Diagnosis and treatment are best performed in a multidisciplinary centre of expertise.