SYNGAP1 and dopa-responsive dystonia due to sepiapterin reductase deficiency: Since the initial discovery of SYNGAP1 and its association to NSID, epilepsy, and ASD in 2009, natural history studies of SRD have been published over the last decade, with studies such as Vlaskamp et al. 2018 (n = 57 SRD patients) and [17] (n = 147 SRD patients).