 Decreases in Hh| production disturb the production of extracellular signal-regulated kinases, bone morphogenetic proteins, and fibroblast growth factors, all of which play important roles in craniofacial patterning.Disruption of these pathways leads to abnormal bone and cartilage formation causing acrania and multiple other craniofacial patterning problems.Little genetic counseling can be offered for acrania because the genetic origins are not fully understood.