If the Shimomura et al. paper is treated as a screen, this represents (counting homozygous recessive individuals) case+: 1 and case-: 1. Adding the Naeem et al control+: 0, control-: 200, this has a significance of p = 0.0099 and a very high OR.
GET-Evidence finds of 5 out of 114 random control chromosomes have this variant, predicting that at least 0.2% of the population is homozygous for this variant. This is much higher than the incidence of ectodermal dysplasia, which may be around .02-.01% (1 or 2 in 10,000), significantly contradicting a severe pathogenic effect.