AQP4 and myeloid sarcoma: This apparent paradox, where the C allele of the AQP4 rs335929 polymorphism within a rs2075575 (A)-rs162009 (A)-rs335929 (C) (A-A-C) haplotype is associated with an increased risk for MS yet correlates with better rehabilitation outcomes, may be explained by pleiotropic and context-dependent mechanisms.