King-Denborough Syndrome-Dysmorphic Features Suggesting Risk of Malignant Hyperthermia
Abstract
Background
King-Denborough syndrome is a rare disorder within the spectrum of RYR1-related myopathies. It is a congenital myopathy, with characteristic dysmorphic features, and susceptibility to malignant hyperthermia. Early recognition is clinically important because the diagnosis may affect anesthetic management and perioperative safety.
Case presentation
We report a 4.5-year-old boy with delayed motor development, generalized hypotonia, characteristic dysmorphic features, and mildly elevated serum creatine kinase levels. The MRI showed features of asymmetrical atrophy and fatty degeneration in the proximal muscles of the lower limbs.
Results
Molecular testing identified a heterozygous RYR1 variant. In the context of the clinical phenotype and muscle imaging findings, the presentation was considered suggestive of King-Denborough syndrome within the spectrum of RYR1-related disorders.
Conclusion
This case highlights the importance of another RYR1-related myopathy in children presenting with myopathic features, dysmorphism, and muscle MRI abnormalities. Recognition of this phenotype is particularly important because of the potential risk of malignant hyperthermia and the need for appropriate anesthetic precautions.
© 2026 Piotr Nowakowski, Karolina Czeczko, Anna Potulska-Chromik, Justyna Żelewska, Aleksandra Jastrzębska, Anna Wójcicka, Paweł Gaj, Anna Kostera-Pruszczyk, published by Institute of Mother and Child
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