Another patient, ARG4, carried a homozygous nonsense variant (p.(Tyr123*)) in PACRG. This gene has been implicated in motile cilia function and mutations in mice are known to cause male infertility characterised by defective sperm head and tail formation in combination with hydrocephalus next to fertility problems (Lorenzetti et al., 2004; Wilson et al., 2010; Li et al., 2015). The gene discussed is PACRG; the disease is Hydrocephalus.