There are now up to 52 LDSs, with more being added all the time. Most are due to one single protein deficiency. They are individually rare.  There are some LSD’s where there are only a handful of patients that are described worldwide but if you clump them all together they are pretty frequent, with a prevalence of one in 7,700 to one in 10,000 births. This is changing now with the advent of newborn screening and more population studies. There are also certain ethnic predilections such as sphingolipidoses like Gaucher Disease which is more prevalent in the Ashkenazi jewish population, MPS1 is more prevalent in the Irish travellers, and Pompe Disease in some Asian subpopulations.