Different clinical phenotypes of AQP4-IgG positive NMOSD in two first degree relatives

Neuromyelitis optica spectrum disorder (NMOSD) are autoimmune inflammatory disorders of the CNS in which patients have severe relapses of optic neuritis and myelitis. Aquaporin-4 antibody (AQP4-IgG) positive NMOSD has not been reported in members of the same family in Sub Saharan Africa. We report the uncommon scenario in which both a Ugandan HIV positive woman and her HIV negative daughter were diagnosed with AQP4-IgG positive NMOSD. We discuss pathogenic mechanisms that may underlie familial presentation of AQP4-IgG positive NMOSD.

Case 1, a 54-year-old female teacher with a 20-year history of HIV infection and virally suppressed on Tenofovir, Lamivudine and Dolutegravir HAART regimen, presented with 8 months of progressive quadriparesis and urinary incontinence with a T6 sensory level. She had gadolinium enhancing longitudinally extensive transverse myelitis on MRI and was AQP4-IgG positive on serum studies. She received IV Methylprednisone 1 g daily for 3 days as a pulse and was continued on tapering doses of oral Prednisone with maintenance doses of Azathioprine. She showed slow improvements in limb motor function. Her daughter, case 2, is a 35-year-old HIV negative nutritionist, independently ambulant, with no known comorbidities or precedent autoimmune disease. She presented 1 year before her mother's AQP4-IgG positive NMOSD diagnosis with 7 months history of bilateral visual loss of rapid onset, with gadolinium-enhancing optic nerves on Brain and orbit MRI, in keeping with bilateral optic neuritis. She was AQP4-IgG positive on serum studies. She stabilized on tapered doses of oral Prednisone and continues daily oral Azathioprine with moderate improvement in her vision and no further relapses as yet.

We add to existing literature and hypothesize that NMOSD appears to show a complex genetic background. To our knowledge, this is the first report in Sub-Saharan Africa, of familial AQP4-IgG positive NMOSD presenting with clinical heterogeneity between first degree relatives. A better understanding of the pathogenic mechanisms involved, including genome wide studies for particular risk loci for familial NMOSD, will be pivotal for future preventative and therapeutic strategies.