Neurogenic Heterotopic Ossification: A Rare Complication of Guillain-Barré Syndrome Exacerbated by Ankylosing Spondylitis and HLA-B27.

We report an exceptional case of neurogenic heterotopic ossification (NHO) developing in a 28-year-old female with pre-existing human leukocyte antigen B27 (HLA-B27) positive ankylosing spondylitis (AS), following a severe course of Guillain-Barré syndrome (GBS). Seven days postpartum, she developed acute GBS requiring three months of intensive care, intubation, mechanical ventilation, and plasmapheresis, leading to flaccid tetraplegia and prolonged immobilization. Four months post-GBS onset, she presented with bilateral hip pain and severely restricted range of motion. Radiographs and CT scans confirmed extensive heterotopic ossification around both femoral heads. Biological workup revealed significant elevations in alkaline phosphatase (ALP), C-reactive protein (CRP), and erythrocyte sedimentation rate (ESR), alongside hypercalcemia. This case uniquely highlights the rare occurrence of NHO after GBS (reported in only 6% of GBS patients), compounded by a potential genetic predisposition from HLA-B27-positive AS. We discuss the intricate interplay of neuroinflammation, prolonged immobility, and genetic factors in NHO pathogenesis, emphasizing the diagnostic challenges and the need for a multidisciplinary approach in such complex presentations. This report underscores the importance of considering NHO in GBS patients, especially those with pre-existing inflammatory conditions, and contributes to understanding the broader risk factors for this debilitating complication.