The author presents a boy which has repeated facial palsies since his second year of life. The clinical examination showed: conduction deafness, radiological sclerosis of the bones of the basis of the skull, normal values of chemical blood analysis. Both facial nerves are operated in the mastoid and middle ear portions. The histological examination of the mastoid bone reveals a leontiasis ossea. The histological structure of the bone are described in detail and the differential diagnosis with other bone diseases of the cranial bones is discussed.