Neuromyelitis optica spectrum disorder coexisting with ankylosing spondylitis: A case report

Neuromyelitis optica spectrum disorder (NMOSD) is a relapsing, demyelinating, inflammatory disease associated with aquaporin-4 (AQP4) antibody in the central nervous system. Ankylosing spondylitis (AS), which is closely associated with leukocyte antigen B27 (HLA-B27), is a chronic inflammatory disease that primarily affects the axial skeleton. We describe the case of a 46-year-old Chinese female, with one-year history of optic neuritis, was admitted to our hospital with a complaint of bilateral lower limbs and perineum numbness for one month. AQP4-IgG antibodies were positive in both the serum and cerebrospinal fluid of the patient. Additionally, HLA-B27 was positive in the serum. Contrast-enhanced computed tomography scan revealed bilateral sacroiliitis. Magnetic resonance imaging of the spinal cord showed T2 hyperintense lesions in conus medullaris, C8-T1 and T11 of spinal cord. The patient's symptom improved after twice methylprednisolone and mycophenolate mofetil treatment. To our best knowledge, this is the first reported case of concomitant AQP4-positive NMOSD and HLA-B27-positive AS. Systematic studies on the association of NMOSD and AS are needed to clarify whether this coincidence is just a casual phenomenon or whether it points to a yet undiscovered link.