Wormian Bones

Wormian bones are small intrasutural bones of the skull vault named after Ole Worm (not because of their resemblance to certain non-arthropod invertebrates). They are most commonly found along the lambdoid suture, as in the case shown above. Wormian bones can be seen with:

• Idiopathic: Most common cause.
• Hypothyroidism:
• Cleidocranial dysplasia: Look for incomplete ossification of the clavicle and a bell-shaped thorax.
• Down syndrome:
• Osteogenesis imperfecta:
• Hypophosphatasia:
• Menkes kinky hair syndrome: Metaphyseal flaring, long-bone fractures and wormian bones.
• Progeria: Look for acroosteolysis, hypoplastic facial bones and sinuses, open cranial sutures and fontanelles, coxa valga.
• Pyknodysostosis: Look for open cranial sutures and fontanelles, scaphocephaly, sclerotic vertebrae, fractured long bones, stubby hands, partial agenesis of terminal phalanges (mimics acroosteolysis)
• Hajdu-Cheney syndrome: Look for band-like acroosteolysis, among other findings.

The PORKCHOPS mnemonic, too long to be of any practical use, has been promulgated by some: pyknodysostosis, osteogenesis imperfecta, rickets kinky hair syndrome, cleidocranial dysplasia, hypothyroidism, hypophosphatasia, otopalatodigital syndrome, primary acroosteolysis (Hajdu-Cheney syndrome), pachydermoperiostosis, progeria, syndrome of Down.