Abstract
A 15-year-old boy with quadriplegia and facial dysmorphia was referred to the emergency room. This was his first episode of tetraplegia. One maternal uncle had exhibited the same manifestation 20 years before. Blood test revealed severe hypokalaemia and mild hypocalcaemia. The clinical diagnosis revealed an Andersen-Tawil syndrome. Molecular tools allowed us to make the diagnosis of familial hypokalaemic periodic paralysis type 1 associated with a de novo 22q11.2 microdeletion syndrome. Our case report emphasizes the importance of molecular diagnosis in genetic diseases.