Chromosome: 12p13.33
Locus: LQT8
Gene affected: CACNA1C affecting the Cav1.2 calcium channel.
Protein: voltage-dependent L-type calcium channel subunit alpha-1C
Cases often arise de novo.
Cardiac findings:
(1) QTc > 480 milliseconds
(2) functional 2:1 AV block
(3) bradycardia
(4) tachyarrhythmia
(5) congenital heart defect (patient ductus arteriosus, others)
(6) cardiomyopathy
Findings involving hands and feet:
(1) syndactyly of toes 2 and 3
(2) syndactyly of fingers
(3) joint contractures
Facial findings:
(1) depressed nasal bridge
(2) low-set ears
(3) thin vermilion border of the upper lip
(4) rounded face
(5) baldness at birth and during infancy
(6) small, widely spaced teeth
Neuropsychiatric findings may include:
(1) global developmental delays
(2) autism spectrum disorder
(3) seizures
(4) intellectual disability
(5) hypotonia
Complications may include:
(1) severe hypoglycemia
(2) frequent infections associated with abnormal immune response
