Long QT syndrome in chromosome 7q35q36.3 deletion involving KCNH2 gene: Warning for chlorpheniramine prescription.

Background The deletion of the distal 7q region is a rare chromosomal syndrome characterized by wide phenotypic manifestations including growth and psychomotor delay, facial dysmorphisms, and genitourinary malformations. Methods We describe a 6-year-old child with a 12-Mb deletion of the region 7q35q36.3. Results Among the deleted genes, two genes have cardiac implications: PRKAG2 (OMIM #602743), associated with hypertrophic cardiomyopathy, cardiac conduction disease, and sudden death, and KCNH2 (OMIM #152427), coding for a cardiac potassium channel involved in long QT syndrome, unmasked by the chlorpheniramine treatment. At same time, the SHH gene (OMIM #600725), encoding sonic hedgehog, a secreted protein that is involved in the embryonic development, is deleted. Conclusion Our report underlines potential cardiac complications linked to the common pharmacological treatment in this rare multiorgan and proteiform disease.