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King syndrome: a genetically heterogenous phenotype due to congenital myopathies
D Chitayat1, K A Hodgkinson, O Ginsburg
1Department of Pediatrics, Montreal Children's Hospital, McGill University, Quebec, Canada.
Insights
This study details a unique King syndrome case with hyperextensible joints and cardiac dilation, highlighting the condition's variable presentation. It suggests a link between King syndrome, congenital myopathies, and potential malignant hyperthermia risks.
Area of Science:
- Medical Genetics
- Neurology
- Cardiology
Background:
- King syndrome is a rare genetic disorder characterized by specific facial features, myopathy, and skeletal abnormalities.
- Previous reports describe a consistent set of clinical manifestations, making this case notable for its deviations.
Observation:
- The patient presented with myopathy, kyphoscoliosis, joint contractures, and characteristic facial features of King syndrome.
- Atypical features included hyperextensible joints, normal stature, and pectus excavatum.
- Cardiac examination revealed dilation of ventricles, aorta, and pulmonary artery.
Findings:
- Muscle biopsy showed decreased bulk and tone, but normal collagen and elastin fibers.
- No malignant hyperthermia occurred during anesthesia, though transient creatine kinase (CK) level increases were observed.
- The patient's unique presentation expands the known phenotypic spectrum of King syndrome.
Implications:
- The variable clinical presentation suggests King syndrome may result from diverse congenital myopathies.
- There is likely an increased risk of malignant hyperthermia associated with King syndrome, regardless of specific myopathy.
- Further research is needed to elucidate the genetic underpinnings and precise risks associated with King syndrome.
Abstract:
We report on a patient with myopathy, kyphoscoliosis, joint contractures, and a facial appearance consistent with King syndrome. Unlike other reported cases, our patient had hyperextensible joints, normal stature, and pectus excavatum. The cardiac ventricles, aorta, and pulmonary artery were dilated. Malignant hyperthermia did not occur under anaesthesia although there was a transient increase in CK levels. Muscle bulk and tone were significantly decreased but collagen and elastin fibres were normal. The variable clinical presentation of King syndrome suggests that the manifestations are caused by different congenital myopathies and in all cases there is probably an increased risk of malignant hyperthermia.