Progressive cognitive decline in an adult patient with cleidocranial dysplasia.

Cleidocranial dysplasia is a skeletal disorder characterized by a defective skull and defective clavicles caused by RUNX2, an activator of osteoblast differentiation. Consistent with the expression pattern of RUNX2, this disorder typically affects the skeletal system, but not the central nervous system. A 56-year-old man with the prototypic skeletal defects of cleidocranial dysplasia and a RUNX2 deletion presented with a progressive cognitive decline after the age of 40 years. After a failed cranioplasty during childhood, he had worn a protective helmet until young adulthood. His current neuroimaging studies revealed extensive cystic encephalomalacia beneath the defective skull, suggesting that his cognitive decline could likely be attributed to repetitive cerebral contusions. Late-onset progressive cognitive decline in the context of a defective skull accompanied by extensive cystic encephalomalacia illustrates the importance of natural calvarial protection against head injury. Since the majority of patients with cleidocranial dysplasia do not wear protective helmets beyond childhood, mainly for cosmetic reasons, a discussion of whether the social disadvantage outweighs the potential risk of brain parenchymal injury may be necessary.