Clinical and pathological characteristics of mitochondrial myopathy and the screening value of simplified serum lactic acid exercise test

Abstract

Objective To analyze clinical and pathological characteristics of mitochondrial myopathy (MM) in 15 patients, and to study the value of simplified serum lactic acid exercise test in the screening of mitochondrial myopathy.  Methods A total of 15 patients with mitochondrial myopathy diagnosed clinically and pathologically, 11  patients with other muscular diseases (OM), and 21 normal controls were collected. All subjects went up and down stairs for 5 min with medium effort. Blood samples for serum lactic acid detection were collected from all subjects before exercise, immediately after exercise and 10 min after exercise. Serum lactic acid levels were compared among 3 groups and among 3 time points. Results Patients with mitochondrial myopathy mainly presented as paroxysmally progressive muscular   soreness and weakness. Histopathological examination showed there were 8 cases with the proportion of ragged red fibers (RRF) more than 5%. Serum lactic acid level before exercise, immediately after exercise and 10 min after exercise were (3.57 ± 1.88), (10.98 ± 4.84) and (7.87 ± 4.38) mmol/L in MM group, (1.89 ± 0.98), (6.05 ± 4.07) and (4.13 ± 3.14) mmol/L in OM group, (1.91 ± 0.53), (3.37 ± 1.22) and (2.52 ± 0.89) mmol/L in control group. Serum lactic acid level in MM group was significantly higher than that in control and OM groups before exercise (P = 0.000, 0.001), immediately after exercise (P = 0.000, 0.001), and 10 min after exercise (P = 0.000, 0.003). Serum lactic acid level in OM group was significantly higher than that in control group immediately after exercise (P = 0.042). Serum lactic acid level in 3 groups immediately after exercise (P = 0.000, 0.000, 0.003) and 10 min after exercise (P = 0.000, 0.000, 0.013) was significantly higher than that before exercise. Serum lactic acid level immediately after exercise was significantly higher than that 10 min after exercise in 3 groups (P = 0.000, 0.000, 0.003). Serum lactic acid level had most obvious elevation in MM group, while had flattest elevation in control group.  Conclusions Simplified serum lactic acid exercise test is useful in the  creening of mitochondrial myopathy, especially in primary hospitals.

DOI:10.3969/j.issn.1672-6731.2016.12.009