Pyknodysostosis
Updates to Article Attributes
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.
Pathology
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.
Clinical presentation
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
Radiographic features
Osteosclerosis with narrowed medullary cavities is the main generalised imaging finding. Long bone fractures are common. Obtuse angle of the mandible. Lack / abnormal teeth.
Plain film / CT
Hands
- 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
Other
- sclerosis of vertebral bodies
- increased lumbar lordosis
- vertebral segmentation anomalies particularly upper cervical(C1/2) and lower lumbar(L5/S1)
- hypoplastic clavicles
- erosion of outer end of clavicles
Etymology
Derived from the greek terms pucnos = dense , dys = defective , ostosis = bone conditiion
Differential diagnosis
General considerations include
-
osteopetrosis
- no delayed closure of cranial sutures
- no phalangeal or clavicle hypoplasia
- other sclerosing bone dysplasias
-</ul><h4>Radiographic features</h4><p><a href="/articles/osteosclerosis">Osteosclerosis</a> with narrowed medullary cavities is the main generalised imaging finding. Long bone fractures are common.</p><h5>Plain film / CT</h5><h6>Hands</h6><ul>- +</ul><h4>Radiographic features</h4><p><a href="/articles/osteosclerosis">Osteosclerosis</a> with narrowed medullary cavities is the main generalised imaging finding. Long bone fractures are common. Obtuse angle of the mandible. Lack / abnormal teeth. </p><h5>Plain film / CT</h5><h6>Hands</h6><ul>