Features of bioimpedance investigation in patients with myasthenia gravis

Myasthenia gravis is the most common pathology from the group of neuromuscular synapse diseases. An urgent issue remains the development of a decrease in muscle mass in patients with this disease due to limited physical activity, steroid myopathy, senile sarcopenia, and a number of other factors.
The aim of the study. To identify diff erences in body composition parameters in patients with myasthenia gravis and healthy individuals using bioimpedance measurement.
Materials and methods. The prospective study included 40 patients with myasthenia gravis and 30 people in the control group (healthy volunteers) who underwent anthropometry and analysis of body composition using bioimpedance research.
Results. Patients with  myasthenia gravis showed a  higher body mass index (26.4  ±  5.2 versus 23.9 ±  4.1  kg/m2; p =  0.045), however, the  prevalence of  obesity in  both groups had no  statistically signifi cant diff erences and amounted to 11.1 % among patients with myasthenia gravis and 9.3 % in the control group (p = 0.82). At the same time, the percentage of fat mass was signifi cantly higher in patients with myasthenia gravis: 32.4 ±  6.8 versus 26.1 ±  5.2 % (p = 0.008), and  the proportion of people with excess fat mass was 57.1 % in the main group and 26.1 % in the control group (p = 0.031). In addition, in patients with myasthenia gravis, lean body weight, active cell mass and its proportion in body composition were statistically signifi cantly lower than in the control group: 55.4 ± 6.2 versus 58.7 ± 5.1 kg, 24.1 ± 5.8 versus 28.6 ± 4.7 kg and 44.8 ± 4.3 versus 49.1 ± 3.5 %, respectively. A reduced proportion of active cell mass (less than 50 % in women and less than 53 % in men) was detected in 68 % of patients with myasthenia gravis and only in 20 % of the control group. Similarly, a reduced proportion of musculoskeletal mass – less than 40 % in women and less than 45 % in men – was observed in 54 % of patients with myasthenia gravis versus 13 % in the control group. Bone mineral mass is lower in patients with myasthenia gravis: 2.21 versus 2.53 kg in the control, that is, 0.32 ± 0.19 kg less (p = 0.02). In 32% of patients, bone mineral mass values were lower than the conditional norm (2.0 kg), although this diff erence did not reach the level of statistical signifi cance (p = 0.052).
Conclusion. According to  the  bioimpedance study, patients with myasthenia gravis, compared with healthy volunteers in  the  control group, showed higher body mass index and  fat mass, combined with a decrease in lean, active cellular and musculoskeletal mass, as well as bone mineral mass.

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