Revision 16 for 'Pyknodysostosis'
Pyknodysostosis (osteopetrosis acro-osteolytica) is a rare autosomal recessive bone dysplasia characterised by osteosclerosis and short stature. The condition is also known as Toulouse-Lautrec syndrome, named after the famous French artist who was thought to be afflicted with the disease.
Pyknodyostosis is a lysosomal disorder due to genetic deficiency in Cathepsin K which has been mapped to chromosome 1q21. Cathepsin K is essential for normal osteoclast function.
Patients present in early childhood with :
- short stature particularly limbs
- delayed closure of cranial sutures
- frontal and occipital bossing
- short broad hands and hypoplasia of nails
- multiple long bone fractures following minimal trauma
Osteosclerosis with narrowed medullary cavities is the main generalised imaging finding. Long bone fractures are common.
Plain film / CT
- short, stubby fingers
- partial agenesis / aplasia of terminal phalanges simulating acro-osteolysis
- delayed bone age
Cranial and maxillofacial
- marked delay in sutural closure
- frontoparietal bossing
- calvarial thickening
- wormian bones (lambdoidal region)
- relative proptosis
- nasal beaking
- obtuse mandibular gonial angle often with relative prognathism
- persistence of primary teeth
- sclerosis of vertebral bodies
- increased lumbar lordosis
- vertebral segmentation anomalies particularly upper cervical and lower lumbar
- hypoplastic clavicles
- erosion of outer end of clavicles
Derived from the greek terms pucnos = dense , dys = defective , ostosis = bone conditiion