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Objective To report a family of hypokalaemic periodic paralysis (HypoPP) with muscle atrophy due to SCN4A gene R672G mutation. The clinical, pathological and MRI characteristics of HypoPP were summarized combining literatures review. Methods and Results The proband was a 27⁃year⁃old male patient who firstly presented periodic muscle weakness from 7 years old. The episode frequency increased with age, and gradually accompanied with muscle atrophy and permanent weakness. His mother has the similar episode but lower frequency. Serum potassium level decreased at the episode. The long⁃term EMG showed the compound muscle action potential (CMAP) on ulnar nerve gradually decreased from 0-45 min. The CMAP in abductor digiti minimi was decreased by 75.8% after long⁃time exercise test. Muscle MRI showed edema in vastus lateralis, vastus medialis, gastrocnemius lateralis, gastrocnemius medialis, soleus, et al. Muscle pathology showed eosinophilic light⁃stained sediment under the sarcolemma. Transmission electron microscopy (TEM) showed the sediment under the sarcolemma were primitive myofilaments with disordered arrangement. Gene test showed heterozygous mutation on exon 12 c.2014C＞G (Arg672Gly) in SCN4A gene in proband and his mother. Finally, the proband was diagnosed HypoPP, and the family was confirmed HypoPP due to SCN4A gene R672G mutation. Conclusions HypoPP due to SCN4A gene R672G mutation can have pathological feature of muscle atrophy and sediment of primitive myofilament. The nature of the sediment needs further study.

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 screening of mitochondrial myopathy, especially in primary hospitals. [ABSTRACT FROM AUTHOR]

Background The main clinical manifestations of mitochondrial myopathy are chronic limb weakness and muscular soreness. Subclinical peripheral nerve injury is also reported, but acute axonal neuropathy-like syndrome concurrent with lactic acidosis is rare. In this paper the clinical features of 2 patients presenting as acute lactic acidosis and sudden muscle weakness were analyzed. Pathological changes and genetic mutations were detected. Methods Electromyography (EMG) and muscle biopsy were performed. Modified Gomori trichrome (MGT) and succinodehydrogenase (SDH) staining were used to identify pathological changes. Changes of ultra microstructure of muscular tissue were observed under electron microscope. Mitochondrial DNA (mtDNA) full length sequencing was performed using 24 pairs of partially overlapping primers. Results EMG showed a coexistence of neurogenic and myogenic changes. Dramatic decrease of motor nerve amplitude and moderately reduced sensory nerve amplitude were observed but nerve conduction velocity was normal in both patients. Impressive ragged red fibers were seen on MGT staining. Electron microscope showed dramatic mitochondrial abnormalities in Case 1 and paracrystaline inclusions in Case 2. mtDNA sequencing showed 3243A > G mutation in Case 1 and 8344A > G mutation in Case 2. Conclusions Mitochondrial myopathy can present as metabolic crisis like acute lactic acidosis, dyspnea and acute motor axonal neuropathy-like syndrome. It is a life-threatening phenotype that needs more attention. [ABSTRACT FROM AUTHOR]

Objectives: To confirm the specific decrease of P25 protein, a novel myasthenia gravis (MG) associated protein, in myasthenia gravis (MG) patients and to study the tissue and species specificity of its expression., Methods: Samples of great pectoral muscle were taken from 28 MG patients, 17 males and 11 females, 10 of which being complicated with thymoma and 18 with hyperplasia of thymus, during thymectomy, and 24 wounded persons as normal controls, 14 males and 10 females, during thoracic surgery. Ten samples of skeletal muscle were taken from 10 patients with other muscular disorders (OMD) during skeletal muscle biopsy. Six samples of normal skeletal muscle, smooth muscle, brain, lung, kidney, and skin were taken from persons who died of accident. Two samples of normal cardiac muscle and thymus gland were taken from a patient undergoing cardiac valve replacement. Eight samples of animal skeletal muscle were taken from the thighs of pig, cattle, dog, rabbit, rat, mouse, chicken, and frog. Immunohistochemistry was used to examine the expression of P25 protein in the samples from the MG patients and the normal controls. Western blotting was used to detect the expression of P25 in the samples from MG patients, normal controls, OMD patients, 8 samples of different human tissues, and skeletal muscle samples from 8 different animals., Results: Immunohistochemistry showed that the staining intensity of P25 protein in skeletal muscle of MG patients was much lower than that of the normal controls. Western blotting showed that the relative density value of P25 protein in MG patients was 1.04 +/- 0.18, significantly lower than those in the normal controls and OM patients (1.27 +/- 0.21 and 1.21 +/- 0.15 respectively. P < 0.01 and P < 0.05). No statistically significant difference in expression of P25 protein was found among different clinical and pathological types of MG patients. Among the 8 human tissues P25 protein was expressed only in skeletal muscle and among the 8 animal samples of skeletal muscle P25 protein expression was found only in swine skeletal muscle., Conclusion: The expression of P25 protein is significantly decreased in skeletal muscle of MG patients. The expression of P25 protein is tissue- and species specific.