Major motor-functional determinants associated with poor self-reported health-related quality of life in myasthenia gravis patients

Myasthenia gravis (MG) is an autoimmune neuromuscular disorder in which disabling muscle weakness may affect health-related quality of life (HRQoL). The aim of this study was to investigate which common motor-functional deficits and corresponding severity are most determinant of poor HRQoL in these patients. In 41 patients, the dichotomized first item of the Italian Myasthenia Gravis Questionnaire (IMGQ), categorizing patients who report "good" and "poor" HRQoL, was chosen as dependent-outcome variable. All items composing the myasthenia gravis-specific scale (MG-ADL), i.e. talking, chewing, swallowing, breathing, impairment of ability to brush teeth or comb hair, impairment of ability to rise from chair, double vision, and eyelid droop were acquired as independent variables and dichotomized. Stepwise backward LR multivariable logistic regression analysis was performed. In addition, the main characteristics of patients were compared. MG-ADL items "chewing" >= 1, i.e. "fatigue chewing solid food", and "breathing" >= 2, i.e. "shortness of breath at rest" proved to be significant determinants. Higher dose of corticosteroid therapy was significantly (p = 0.027; r(s) = -0.35), correlated with poor HRQoL. At diagnosis, a decremental response to repetitive nerve stimulation (RNS) from the abductor pollicis brevis was significantly more frequent in patients with poor HRQoL. In conclusion, impaired "chewing" and "breathing" functions indicate the need for careful planning of rehabilitation, re-education and patient management. Moreover, decremental response to RNS at diagnosis may identify patients at risk for poor HRQoL.