RASA1 and congenital myasthenic syndrome: In addition to having CMs, 23% of patients with RASA1 mutations have fast‐flow vascular anomalies: AVM, AVF or Parkes Weber syndrome (PKWS).2, 4, 6 AVMs are rare, fast‐flow anomalies that can cause fatal complications such as bleeding, congestive cardiac failure or neurological deficit.