Phelan-McDermid Syndrome

A rare genetic condition caused by a deletion or other structural change of the terminal end of chromosome 22 in the 22q13 region or a disease-causing mutation of the SHANK3 gene. Although the range and severity of symptoms may vary, people who have PMS often have hypotonia (low or weak muscle tone) and developmental delay (not achieving developmental milestones such as rolling over, sitting up, walking, or talking as early as expected). Less frequently, children may present with heart defects (such as a hole in the heart) or kidney defects which are usually not life-threatening. As children grow, additional symptoms develop including moderate to severe developmental and intellectual impairment, inability to acquire functional language, and about 75% have been diagnosed with an autism spectrum disorder. Behavioral issues may stem from autism (e.g., repetitive behaviors), from poor communications skills, or from an unknown origin. Sleep disorders are commonly reported, as are difficulties with toilet training, and problems with swallowing and eating. About 40% of people develop seizures which can range from mild to severe. Other symptoms include low perception of pain, low perspiration levels which may cause the body to overheat, and the need for protection against direct sunlight and dehydration. Despite these medical and developmental issues, infants with PMS tend to be easily amused, and adults often have a sweet disposition.