<s>[INST] <<SYS>> This is a medical question of type : frequency <</SYS>> How many people are affected by Shprintzen-Goldberg syndrome ? [/INST] Shprintzen-Goldberg syndrome is a rare condition, although its prevalence is unknown. It is difficult to identify the number of affected individuals, because some cases diagnosed as Shprintzen-Goldberg syndrome may instead be Marfan syndrome or Loeys-Dietz syndrome, which have overlapping signs and symptoms. </s>