IgG4-Related Disease Strikes the Cervical Spine: First Description of a Rare Cause for C1 Destruction and Tetraparetic Stenosis

Background and Clinical Significance: Immunoglobulin G4-related disease (IgG4-RD) is a systemic immune-mediated fibroinflammatory disorder that can mimic infection or malignancy. Spinal involvement is exceedingly rare and usually limited to pachymeningitis or epidural pseudotumors. True vertebral bone destruction has been reported only sporadically. Case Presentation: A 54-year-old man presented to our emergency department with severe neck pain after a fall. CT and MRI revealed extensive osteolysis of the C1 posterior arch and odontoid process with atlantoaxial subluxation. Following a second inpatient fall, he developed acute tetraparesis. Emergency posterior occipitocervical fusion (C0–C4) with C1–C2 laminectomy and foramen magnum decompression was performed. Histopathology demonstrated dense lymphoplasmacytic infiltration and fibrosis with up to 36 IgG4+ plasma cells per high-power field and an IgG4+/IgG ratio > 40%, confirming IgG4-RD. The patient recovered substantial motor function postoperatively and regained independent ambulation after neurological rehabilitation. Conclusions: IgG4-RD can rarely present as destructive craniovertebral osteolysis with neurological compromise. Unexplained C1–C2 osteolytic lesions should prompt evaluation for IgG4-RD, a rare but treatable cause of cervical instability.