This letter was referred to Dr. Michael R. Nihill, who replies in this manner:
We appreciate the letter from Dr. Boccuzzi and colleagues noting the association of trisomy 21 with an isolated cleft of the mitral valve as described in our paper.1 While the isolated cleft is anatomically different from the cleft or commissure seen in endocardial cushion defects, both defects are closely related, embryologically, to the maturation of the endocardial cushions in the formation of the atrioventricular junction. As noted in their reference (Cousineau, et al.2) an endocardial cushion defect gene might not be associated with the 21st chromosome and trisomy 21. Further studies of familial endocardial cushion defects are needed to elucidate this point.
Michael R. Nihill, MD
Section of Pediatric Cardiology, Texas Children's Hospital, Houston, Texas
References
- 1.Zhu D, Bryant R, Heinle J, Nihill MR. Isolated cleft of the mitral valve: clinical spectrum and course. Tex Heart Inst J 2009;36(6):553–6. [PMC free article] [PubMed]
- 2.Cousineau AJ, Lauer RM, Pierpont ME, Burns TL, Ardinger RH, Patil SR, Sheffield VC. Linkage analysis of autosomal dominant atrioventricular canal defects: exclusion of chromosome 21. Hum Genet 1994;93(2):103–8. [DOI] [PubMed]