LAUSR

BACKGROUND The majority of the abnormalities and diseases that affect the craniovertebral junction (CVJ) have already been reported, and therefore it is exceedingly rare to identify new pathology that affects the CVJ. IgG4 related disease (IgG4-RD) is an immune mediated process treated with immunosuppressive medications. This is the first reported case of IgG4-RD affecting the CVJ. CASE DESCRIPTION The authors report the case of a 71-year-old woman with IgG4-RD of the CVJ. She presented with intractable left occipital pain and limited flexion, extension and rotation of the neck. CT and MRI revealed a lytic enhancing lesion of the left occipital condyle, left C1 lateral mass, and left C1 anterior arch resulting in cranial settling, basilar invagination, and CVJ instability. An open biopsy, subtotal resection, and occiput to C2 fusion was performed. Pathology revealed IgG4-RD. The patient was subsequently placed on rituximab immunotherapy with complete resolution of enhancement on MRI and bone growth at the previous site of the lytic IgG4-RD lesion. CONCLUSION This case describes the first case of IgG4-RD affecting the CVJ, which mimicked a tumor-like process. When IgG4-RD affects the CVJ, stability must be accounted for, especially in the cases of osteolytic destruction. The combination of medical therapy to target the underlying inflammatory process and surgery to provide structural stability was successful.