Back to Health A to Z Differences in sex development Differences in sex development DSD is a group of rare conditions involving genes, hormones and reproductive organs, including genitals. It means a person's sex development is different to most other people's. Some adults and young people with DSD prefer to use the term intersex. Why does DSD happen? You or your child may have sex chromosomes bundles of genes usually associated with being female XX chromosomes or usually associated with being male XY chromosomesbut reproductive organs and genitals that may look different from usual. This happens because of a difference with your genes or how you respond to the sex hormones in your body, or both.