Intraoperative Presentation of Malignant Hyperthermia (Confirmed by RYR1 Gene Mutation, c.7522C>T; p.R2508C) Leads to Diagnosis of King-Denborough Syndrome in a Child With Hypotonia and Dysmorphic Features: A Case Report.

We present the novel case report of a child with hypotonia and dysmorphic features who developed malignant hyperthermia (MH) intraoperatively. Neurology workup revealed the presence of a known causative ryanodine receptor (RYR1) mutation for MH, c.7522C>T; p.R2508C. Furthermore, the neurology workup diagnosed the child with King-Denborough syndrome (KDS). This particular mutation has never been documented in a patient with KDS. Atypical presentation of MH is more likely in patients with RYR1-related myopathy. A high index of suspicion for MH in children with myopathy is important. The MH hotline was helpful in the management of this patient when it was called after the initial dose of dantrolene. A neurology consult was essential for the diagnosis of KDS and future care.