AQP4 and systemic mastocytosis: In parallel, venous thromboembolism (VTE) has been reported mainly in NMOSD patients exhibiting transverse myelitis.<h4>Case presentation</h4>Here, we describe an Aquaporin-4 positive (AQP4-positive) NMOSD patient who showed short myelitis (SM) and experienced a fatal pulmonary thromboembolism/lower extremity deep vein thrombosis during anti-CD20 treatment.