ABSTRACT
It is generally accepted that there are around 10,000 human diseases associated with variations in single genes (“monogenetic diseases”) (WHO 2015; Kingsmore et al. 2011). Many of the genetic diseases known or suspected are rare or “ultra-rare” (by defi nition, rare diseases occur in fewer than 1 in 2,000 people, ultra-rare diseases in fewer than 1 in 2,000,000) (Hennekam 2011), but the total burden of such genetic diseases is signifi cant, with researchers estimating that around 1% of the population, on average, has at least one condition associated with a single-gene disorder, and perhaps 4-10% of all pediatric hospital admissions are the result of single-gene disorders or chromosomal abnormalities (Dye et al. 2011; Kingsmore et al. 2011).
