Novel genetic variants of the Bone Morphogenetic Protein Receptor, Type II (Serine/Threonine Kinase) (BMPR2) gene are described. Various genotypes, haplotypes, and haplotype pairs that exist in the general United States population are disclosed for the BMPR2 gene. Compositions and methods for haplotyping and/or genotyping the BMPR2 gene in an individual are also disclosed. Polynucleotides defined by the haplotypes disclosed herein are also described.