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.