Normal IQ is possible in Smith-Lemli-Opitz syndrome.
Eroglu Y, Nguyen-Driver M, Steiner RD, Merkens L, Merkens M, Roullet JB, Elias E, Sarphare G, Porter FD, Li C, Tierney E, Nowaczyk MJ, Freeman KA. Normal IQ is possible in Smith-Lemli-Opitz syndrome. Am J Med Genet A. 2017 Aug; 173(8):2097-2100.