X-linked dominant disorders are unusual. Both males and females are affected. In X-linked dominant disorders, a female carrying the mutation will be affected while the mutation carrying males have an even more serious condition. For example, a mutation that causes Rett syndrome (a neurodegenerative disorder) in a girl will cause a lethal, neonatal-onset encephalopathy in males. An example is hypophosphataemic (vitamin D-resistant) rickets.