ossification of the posterior longitudinal ligament of the spine

ossification of the posterior longitudinal ligament of the spine

A common (up to 4% in Asians) autosomal recessive myelopathy (OMIM:602475), which can cause spinal-cord compression leading to tetraparesis.
 
Imaging
Dagger sign is typically seen in T4-T7.

Molecular pathology
OPLL is cause by:
(1) A defect of COL6A1, which encodes collagen VI, a cell binding collagen; and
(2) Loss of function mutations in ENPP1, which encodes a transmembrane glycoprotein that regulates soft tissue calcium and bone and joint cartilage mineralisation by generating pyrophosphate (PPi), a physiological inhibitor of hydroxyapatite crystal formation and a suppressor of chondrogenesis.
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