However, the levels of BDNF and GDNF in the CSF were below the limit of sensitivity of the methods used.Our findings of mainly normal CSF NGF in autism, low to negligible values in RTT, decreased IGF-1 in autism and normal values in RTT, agree with the different morphological and neurochemical findings in the two syndromes [97]. The gene discussed is GDNF; the disease is autism.