AQP4 and arthritic joint disease: The most common clinical manifestations in the studied patients were renal involvement (73.3%), neurological disorders, arthritis (65.6%), cardiac affection (57.8%), and serositis (51.1%), with a significantly higher frequency of renal involvement, neuropsychiatric disorders and cardiac affection in the AQP4-IgG Ab-positive subgroup than in the AQP4-IgG Ab-negative subgroup (P = 0.004, 0.001, 0.04, and 0.013, respectively) (data not shown in table).