Pyknodysostosis
Updates to Article Attributes
Pyknodysostosis, also known as osteopetrosis acro-osteolytica or Toulouse-Lautrec syndrome, is a rare autosomal recessive bone dysplasia, characterised by osteosclerosis and short stature.
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
Pathology
Pyknodysostosis 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.
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 radiograph / 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
- vertebral body sclerosis
- increased lumbar lordosis
- vertebral segmentation anomalies particularly upper cervical (C1 and C2) and lower lumbar (L5 and S1)
- hypoplastic clavicles
- erosion of distal clavicles
History and etymology
Derived from the greek terms "pucnos" (dense), "dys" (defective) and "ostosis"(bone condition).
"Acro" in osteopetrosis acro-osteolytica is Ancient Greek for "at the extremity" and refers to resorption at the distal phalanges as observed in this condition.
The condition is also known as Toulouse-Lautrec syndrome, named after the famous French artist Henri Marie Raymond de Toulouse-Lautrec-Monfa (1864-1901) who was thought to be afflicted with the disease.
Differential diagnosis
General imaging differential considerations include:
-
osteopetrosis
- "bone in bone" appearance
- no delayed closure of cranial sutures
- no phalangeal or clavicle hypoplasia
- other sclerosing bone dysplasias
-<li>partial agenesis/aplasia of terminal phalanges, simulating <a href="/articles/acro-osteolysis-1">acro-osteolysis</a>-</li>- +<li>partial agenesis/aplasia of terminal phalanges, simulating <a href="/articles/acro-osteolysis-1">acro-osteolysis</a> </li>
-</ul><h4>History and etymology</h4><p>Derived from the greek terms "pucnos" (dense), "dys" (defective) and "ostosis"(bone condition). </p><p>The condition is also known as <strong>Toulouse-Lautrec </strong>syndrome, named after the famous French artist <strong>Henri Marie Raymond de Toulouse-Lautrec-Monfa</strong> (1864-1901) who was thought to be afflicted with the disease.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include:</p><ul>- +</ul><h4>History and etymology</h4><p>Derived from the greek terms "pucnos" (dense), "dys" (defective) and "ostosis"(bone condition). </p><p>"Acro" in osteopetrosis acro-osteolytica is Ancient Greek for "at the extremity" and refers to resorption at the distal phalanges as observed in this condition. </p><p>The condition is also known as <strong>Toulouse-Lautrec </strong>syndrome, named after the famous French artist <strong>Henri Marie Raymond de Toulouse-Lautrec-Monfa</strong> (1864-1901) who was thought to be afflicted with the disease.</p><h4>Differential diagnosis</h4><p>General imaging differential considerations include:</p><ul>