Treff and colleagues [109] evaluated NGS-based PGD for single gene disorders in six couples at-risk of transmitting either autosomal recessive disease (Walker Warburg syndrome, cystic fibrosis, familial dysautonomia), dominant disease (neurofibromatosis 1) or X-linked hypophosphatemic rickets to their children. The gene discussed is NF1; the disease is X-linked hypophosphatemic rickets.