Home Pycnodysostosis


Defining Characteristics

Disproportionate (big head, small body), pectus excavatum, lumbar lordosis, nail hypoplasia (missing nails)
Facial dysmorphism? Missing jaw look, large forehead, underdeveloped nose, asymmetry

Disease Development

Mutation/defect in cathepsin K, so osteoclasts can no longer function properly in bone resorption

Potential Causes

Bone overgrowth due to loss of osteoclast resorptive fx


Onset in infancy, early childhood
Very rare!


XR? Dense orbital ridge, sclerotic skull base, hypoplasia of facial bones, dense vertebrae w/ preservation of TVP


Recurrent fractures in lower limbs