Wormian bones are seen in -

Wormian bones Wormian bones are extra bone pieces that occur within a suture in the cranium. These are irregular isolated bones which appear in addition to the usual centres of ossification of the cranium. They occur most frequently in the course of the lambdoid suture. Causes of wormian bones (Mnemonic - PORKCHOPS) Pyknodysostosis Osteogenesis imperfecta Rickets Kinky hair syndrome Cleidocranial dysostosis Hypothyroidism (cretinism) / Hypophosphatasia Otopalatodigital syndrome Progeria Syndrome of Downs Wormian bone appears radiographically as islands of ossification in the skull in nonossified membranous bone. To be diagnostic value, the wormian bones should be 4 mm by 6 mm in size, 10 in number and arranged in a mosaic pattern. Wormian bones are not present in the normal skull.