Characteristics of South Korean Patients with Hereditary Transthyretin Amyloidosis.

BACKGROUND AND PURPOSE: This retrospective cross-sectional study included 18 patients from unrelated families harboring mutations of the transthyretin gene (TTR), and analyzed their characteristics and geographical distribution in South Korea. METHODS: The included patients had a diagnosis of systemic amyloidosis, clinical symptoms, such as amyloid neuropathy or cardiomyopathy, and confirmation of a TTR gene mutation using genetic analysis recorded between April 1995 and November 2014. RESULTS: The mean age at disease onset was 49.6 years, and the mean disease duration from symptom onset to diagnosis was 3.67 years. Fifteen of the 18 patients were classified as mixed phenotype, 2 as the neurological phenotype, and only 1 patient as the cardiac phenotype. The most-common mutation pattern in South Korea was Asp38Ala, which was detected in eight patients. Thirteen patients reported their family hometowns, and five of the eight harboring the Asp38Ala mutation were from the Gyeongsang province in southeast Korea. The other eight patients exhibited a widespread geographical distribution. A particularly noteworthy finding was that the valine at position 30 (Val30Met) mutation, which was previously reported as the most-common TTR mutation worldwide and also the most common in the Japanese population, was not detected in the present South Korean patients. CONCLUSIONS: South Korean patients with hereditary TTR amyloidosis exhibited heterogeneous TTR genotypes and clinical phenotypes. The findings of this study suggest that the distribution of TTR amyloidosis in South Korea is due to de novo mutations and/or related to the other countries in East Asia.

3,4-Diaminopyridine for the treatment of myasthenia gravis with electrophysiological patterns of Lambert-Eaton myasthenic syndrome.

3,4-Diaminopyridine (34DAP) is a presynaptic transmission enhancer. Its efficacy for Lambert-Eaton myasthenic syndrome (LEMS) and myasthenia gravis (MG) was demonstrated. However, there are cases sharing the characteristics of both disease and the effect of 34DAP in "gray zone" patients is sparse. Recently, we prescribed 34DAP to five anti-acetylcholine receptor antibody-positive MG patients with electrophysiological LEMS patterns and three LEMS patients, and carefully monitored the responses. Sero-positive MG patients exhibited more favorable responses than LEMS patients. The combination of 34DAP and pyridostigmine resulted in the best outcomes. No significant side effects were recorded during the follow-up period. In conclusion, this study results provide evidence that 34DAP could be effective in sero-positive MG patients with pre-synaptic dysfunction.

Repetitive Nerve Stimulation in MuSK-Antibody-Positive Myasthenia Gravis.

BACKGROUND AND PURPOSE: Responses to repetitive nerve stimulation (RNS) in patients with muscle-specific tyrosine kinase (MuSK) antibody (Ab)-positive myasthenia gravis (MG) vary depending on the muscles tested. We analyzed the RNS responses of limb and facial muscles in MuSK-Ab-positive and acetylcholine receptor (AChR)-Ab-negative MG (MuSK MG) and MuSK-Ab-negative and AChR-Ab-negative [double-seronegative (DSN)] MG patients. METHODS: We retrospectively compared RNS responses between 45 MuSK MG and 29 DSN MG. RNS was applied to the abductor digiti minimi, flexor carpi ulnaris, trapezius, orbicularis oculi, and nasalis muscles. RESULTS: Abnormal RNS responses in limb muscles were observed in 22.2 and 58.6% of MuSK MG and DSN MG patients, respectively, with abnormal facial responses observed in 77.8 and 65.5%, and abnormal responses observed in any of the five muscles in 86.7 and 72.4%. Abnormal RNS responses in the abductor digiti minimi or flexor carpi ulnaris were less frequent in MuSK MG (8.9 and 15.6%, respectively) than in DSN MG (37.9 and 55.2%), whereas the findings for other muscles were not significantly different between the groups. Abnormal facial responses but normal limb responses were independently associated with MuSK MG (odds ratio=5.224, 95% confidence interval=1.300-20.990). CONCLUSIONS: Abnormal RNS responses primarily in facial muscles without involvement of limb muscles were more pronounced in MuSK MG than in DSN MG. RNS of both facial and limb muscles in AChR-Ab-negative MG can increase the test sensitivity and aid in early suspicion of MuSK MG.

Juvenile Myasthenia Gravis in Korea: Subgroup Analysis According to Sex and Onset Age.

Juvenile myasthenia gravis presents before 18 years of age with different characteristics according to racial background and pubertal development. The authors aimed to determine the clinical characteristics of children and adolescents of Korean ethnicity with myasthenia gravis, and evaluate the presentation and clinical outcomes according to the sex and onset age of the patients. The authors recruited 88 Korean juvenile myasthenia gravis patients between September 2005 and August 2015. Worse clinical severity from presentation, more aggressive treatment strategies, and worse final treatment outcomes were noted in girls with postpubertal onset than in the other patients. The symptoms were milder (pure ocular presentation in 96.6% [85/88]) and the disease course was more benign (94.3% [83/88]) in this study than in the literature. The homogenous racial background might have contributed to these results. These findings highlight the influence of pubertal development and the need for timely and appropriate active treatment, including thymectomy, to improve prognosis.

Decremental responses to repetitive nerve stimulation in x-linked bulbospinal muscular atrophy.

BACKGROUND AND PURPOSE: X-linked bulbospinal muscular atrophy (X-BSMA) is characterized by bulbar and spinal muscular weakness and fasciculations. Although X-BSMA is a motor neuronopathy, there are several reports of myasthenic symptoms or decremental responses to repetitive nerve stimulation (RNS). We report the results of applying the RNS test to 15 patients among 41 with genetically confirmed X-BSMA; these 15 patients complained of fatigue, ease of becoming tired, or early muscular exhaustion. METHODS: The 3-Hz RNS test was performed on the trapezius, nasalis, orbicularis oculi, flexor carpi ulnaris, and abductor digiti quinti muscles. A decrement greater than 10% was considered abnormal. Additionally, a pharmacologic response to neostigmine was identified in three patients. RESULTS: A significant decrement was observed in 67% of patients, and was most common in the trapezius muscle (nine cases). The decrement of the trapezius muscle response ranged from 15.9% to 36.9%. The decrement was inversely correlated with the amplitude of compound muscle action potentials at rest. Neostigmine injection markedly improved the decrement in three patients, who showed noticeable decremental responses to 3-Hz RNS. CONCLUSIONS: This study shows that myasthenic symptoms and abnormal decremental responses to low-rate RNS are common in X-BSMA.

Altered fast and slow inactivation of the N440K Nav1.4 mutant in a periodic paralysis syndrome.

OBJECTIVE: To electrophysiologically characterize the Na(v)1.4 mutant N440K found in a Korean family with a syndrome combining symptoms of paramyotonia congenita, hyperkalemic periodic paralysis, and potassium-aggravated myotonia. METHODS: We characterized transiently expressed wild-type and mutant Na(v)1.4 using whole-cell voltage-clamp analysis. RESULTS: N440K produced a significant depolarizing shift in the voltage dependence of fast inactivation and increased persistent current and acceleration in fast inactivation recovery, which gave rise to a 2-fold elevation in the dynamic availability of the mutant channels. In addition, the mutant channels required substantially longer and stronger depolarization to enter the slow-inactivated state. CONCLUSIONS: N440K causes a gain of function consistent with skeletal muscle hyperexcitability as observed in individuals with the mutation. How the same mutation results in distinct phenotypes in the 2 kindreds remains to be determined.

Comparison between clinical disabilities and electrophysiological values in Charcot-Marie-Tooth 1A patients with PMP22 duplication.

BACKGROUND AND PURPOSE: Charcot-Marie-Tooth disease (CMT) type 1A (CMT1A) is the demyelinating form of CMT that is significantly associated with PMP22 duplication. Some studies have found that the disease-related disabilities of these patients are correlated with their compound muscle action potentials (CMAPs), while others have suggested that they are related to the nerve conduction velocities. In the present study, we investigated the correlations between the disease-related disabilities and the electrophysiological values in a large cohort of Korean CMT1A patients. METHODS: We analyzed 167 CMT1A patients of Korean origin with PMP22 duplication using clinical and electrophysiological assessments, including the CMT neuropathy score and the functional disability scale. RESULTS: Clinical motor disabilities were significantly correlated with the CMAPs but not the motor nerve conduction velocities (MNCVs). Moreover, the observed sensory impairments matched the corresponding reductions in the sensory nerve action potentials (SNAPs) but not with slowing of the sensory nerve conduction velocities (SNCVs). In addition, CMAPs were strongly correlated with the disease duration but not with the age at onset. The terminal latency index did not differ between CMT1A patients and healthy controls. CONCLUSIONS: In CMT1A patients, disease-related disabilities such as muscle wasting and sensory impairment were strongly correlated with CMAPs and SNAPs but not with the MNCVs or SNCVs. Therefore, we suggest that the clinical disabilities of CMT patients are determined by the extent of axonal dysfunction.

Heterogeneous characteristics of Korean patients with dysferlinopathy.

Dysferlinopathy is caused by mutations in the DYSF gene. To characterize the clinical spectrum, we investigated the characteristics of 31 Korean dysferlinopathy patients confirmed by immunohistochemistry. The mean age of symptom onset was 22.23 ± 7.34 yr. The serum creatine kinase (CK) was highly increased (4- to 101-fold above normal). The pathological findings of muscle specimens showed nonspecific dystrophic features and frequent inflammatory cell infiltration. Muscle imaging studies showed fatty atrophic changes dominantly in the posterolateral muscles of the lower limb. The patients with dysferlinopathy were classified by initial muscle weakness: fifteen patients with Miyoshi myopathy phenotype (MM), thirteen patients with limb girdle muscular dystrophy 2B phenotype (LGMD2B), two patients with proximodistal phenotype, and one asymptomatic patient. There were no differences between LGMD2B and MM groups in terms of onset age, serum CK levels and pathological findings. Dysferlinopathy patients usually have young adult onset and high serum CK levels. However, heterogeneity of clinical presentations and pathologic findings upon routine staining makes it difficult to diagnose dysferlinopathy. These limitations make immunohistochemistry currently the most important method for the diagnosis of dysferlinopathy.

Sequential involvement of the nervous system in subacute combined degeneration.

PURPOSE: Subacute combined degeneration (SCD) involves progressive degeneration of the spinal cord, optic nerve, and peripheral nerves. Vitamin B12 (VB12) is a co-factor in myelin synthesis. Because each cell that constitutes the myelin component in the central nervous system and peripheral nervous system is different, it is improbable that these cells undergo simultaneous degeneration. However, the sequence of degeneration in SCD has not been established. MATERIALS AND METHODS: In this study, we analysed medical records and electrophysiological data of patients who showed neurological symptoms and whose serum VB12 levels were lower than 200 pg/mL. RESULTS: We enrolled 49 patients in this study. Their mean VB12 level was 68.3 pg/mL. Somatosensory evoked potential (SEP) study showed abnormal findings in 38 patients. Of the 40 patients who underwent visual evoked potential (VEP) study, 14 showed abnormal responses. Eighteen patients showed abnormal findings on a nerve conduction study (NCS). In this study, abnormal posterior tibial nerve SEPs only were seen in 16 patients, median nerve SEPs only were seen in 3 patients, abnormal VEPs only in two, and abnormal NCS responses in one patient. No patient complained of cognitive symptoms. CONCLUSION: In SCD, degeneration appears to progress in the following order: lower spinal cord, cervical spinal cord, peripheral nerve/optic nerve, and finally, the brain.

A case of acute polyneuropathy with nephrotic syndrome showing transient proximal sensory conduction defects.

Acute sensorimotor polyneuropathy that resembles Guillain-Barré syndrome (GBS) is rarely accompanied with nephrotic syndrome, and its underlying immunological mechanisms are unclear. A 56-year-old man presented with simultaneous acute progressive symmetric sensorimotor polyneuropathy and proteinuria. A kidney biopsy revealed focal segmental glomerulosclerosis. Serial electrophysiologic studies showed only a transient proximal conduction block in the median nerve, stimulated somatosensory evoked potential and prolonged terminal latencies of the median and peroneal nerves. The patient's neurologic deficits and kidney dysfunction recovered with corticosteroid treatment. Our case showed that somatosensory evoked potential study can be an important objective tool in the diagnosis of acute polyneuropathy with normal distal nerve conduction and that corticosteroids should be considered in the initial treatment of GBS-resembling polyneuropathy associated with nephrotic syndrome.

Insulin resistance is independently associated with peripheral and autonomic neuropathy in Korean type 2 diabetic patients.

In addition to chronic hyperglycemia, insulin resistance itself has been proposed to cause a diabetic neuropathy. We evaluated the role of insulin resistance in the pathogenesis of peripheral and autonomic neuropathy in patients with type 2 diabetes. Eighty-six patients with type 2 diabetes were evaluated for the anthropometric and biochemical profiles, and Kitt value was calculated from insulin tolerance test to assess the insulin resistance. Various autonomic function tests, nerve conduction velocity, and quantitative sensory tests were performed to assess autonomic and peripheral neuropathy. In univariate analysis, both autonomic and peripheral neuropathy were significantly associated with glycemic exposure index (GE index), HDL-cholesterol, duration of DM, and Kitt value. In stepwise linear regression analysis, GE index was an independent predictor of autonomic and peripheral neuropathy (ß = 0.643, P < 0.001; ß = 0.207, P = 0.013, respectively), and Kitt value was also an independent factor for the autonomic and peripheral neuropathy (ß = - 0.306, P < 0.001; ß = - 0.329, P < 0.001, respectively). Low HDL-cholesterol increased the odds ratio for peripheral neuropathy. Insulin resistance is independently associated with peripheral and autonomic neuropathy in Korean Type 2 diabetic patients along with hyperglycemia and HDL-cholesterol.

A case of lambert-eaton myasthenic syndrome with small-cell lung cancer and transient increase in anti-acetylcholine-receptor-binding antibody titer.

BACKGROUND: Lambert-Eaton myasthenic syndrome (LEMS) is a presynaptic neuromuscular junction disorder that is most frequently associated with small-cell lung cancer (SCLC). The titers of antibodies against voltage-gated calcium channels are frequently increased in LEMS, but only rarely is titer of anti-acetylcholine-receptor-binding antibodies (AChR-abs) increased. CASE REPORT: A 57-year-old male was admitted to our hospital due to dry mouth and eyes and progressive proximal limb weakness of 2 months duration. The results of a repetitive nerve stimulation test disclosed all criteria for the electrophysiological LEMS pattern, and the patient's AChR-abs titer was 0.587 nmol/L. At a follow-up performed 5 years after successful treatment of SCLC and LEMS, his AChR-abs titer had decreased to 0.001 nmol/L. CONCLUSIONS: We suggest that this was a case of transient pseudopositivity of AChR-abs in SCLC with LEMS.

Neurogenic muscle hypertrophy in type III spinal muscular atrophy.

Neurogenic muscle hypertrophy is very unusual and has been rarely described. We described a 25-year-old woman presented with proximal muscle weakness with calf muscle hypertrophy. Limb magnetic resonance imaging scans showed increased muscle bulk without fatty changes, and a muscle biopsy revealed prominent hypertrophic type II muscle fibers. A mutation in SMN1 was found in a genetic analysis. This is the first report of neurogenic muscle hypertrophy seen in genetically confirmed spinal muscular atrophy III.

Repetitive nerve stimulation test in amyotrophic lateral sclerosis with predominant oropharyngeal manifestations.

BACKGROUND AND PURPOSE: Amyotrophic lateral sclerosis (ALS) patients display easy fatigability and abnormal decrements on repetitive nerve stimulation (RNS) test of clinically involved limb muscles, which can result in ALS being misdiagnosed as myasthenia gravis. We retrospectively analyzed the RNS tests of ten ALS patients with only or predominant oropharyngeal symptoms without ocular or facial weakness. METHODS: RNS tests were performed on the abductor digiti quinti, flexor carpi ulnaris, orbicularis oculi (OO), nasalis and trapezius muscles at low-rate stimulation frequencies of 3 and 5-Hz. Decrements greater than 10% of the compound muscle action potential amplitude on the fifth stimulation compared to the first was regarded as abnormal. RESULTS: Six patients complained of muscular fatigue or diurnal fluctuation. Among the ten patients, three exhibited abnormal decrements during low-rate stimulation in the facial muscles but not in the limb muscles, two exhibited abnormal decrements in the OO and nasalis muscles, and one exhibited abnormal decrements in the OO muscle. CONCLUSIONS: These findings show that the facial muscles may be involved in some early oropharyngeal forms of ALS, although facial weakness may not be clinically evident. We confirm herein that abnormal decrement of facial muscles to RNS test cannot make a definite diagnose for myasthenia gravis.

Clinical heterogeneity in Korean patients with nemaline myopathy.

PURPOSE: Nemaline myopathy (NM) is a clinical heterogeneous congenital myopathy characterized by the presence of subsarcolemmal or cytoplasmic rod-like structures that call nemaline bodies in the muscle fibers. The purpose of this study was to investigate the clinical diversity and pathological features of Korean patients with NM. MATERIALS AND METHODS: Eight patients underwent analyses of clinical manifestations by a structured protocol. Diagnoses were established by a muscle biopsy. RESULTS: Two patients had the typical congenital type, which exhibited neonatal hypotonia and delayed motor milestone, and five patients had the childhood onset type, which exhibited mild gait disturbance as a first symptom. One patient had the adult onset type, which showed acute respiratory failure. Limb weakness was proximal-dominant occurred in six patients. Hyporeflexia was observed in most patients. Elongated faces and high arched palates and feet were also observed. On light microscopy, the nemaline bodies were observed in type 1 and 2 fibers. All patients showed type 1 predominance and atrophy. In the two cases in which ultrastructural studies were performed, typical nemaline rods and disorganized myofibrillar apparatus were detected. CONCLUSION: In conclusion, the eight Korean patients in this study with NM shared common clinical expressions such as proximal limb weakness, reduced deep tendon reflex, and dysmorphic features. This study, however, showed that clinical heterogeneity ranged from typical congenital, mildly affected childhood to the adult onset form with acute respiratory failure. The pathological findings in this study were in accordance with those of other previous reports.

Diffuse large B-cell lymphoma presenting as piriformis syndrome.

Piriformis syndrome (PS) is a rare condition characterized by pain and paresthesia of the buttock, often radiating to the posterior thigh. A patient with sciatica that was clinically suspicious for PS, underwent diagnostic work-up. A diagnosis of diffuse large B-cell lymphoma with neurolymphomatosis (NL) was made. To our knowledge, this is the first report of NL presenting as PS. NL is a possible cause of secondary PS.

Clinical characteristics and outcomes of juvenile and adult dermatomyositis.

Dermatomyositis (DM) is an idiopathic inflammatory myopathy with bimodal onset age distribution. The age of onset is between 5-18 yr in juvenile DM and 45-64 yr in adult DM. DM has a distinct clinical manifestation characterized by proximal muscle weakness, skin rash, extramuscular manifestations (joint contracture, dysphagia, cardiac disturbances, pulmonary symptoms, subcutaneous calcifications), and associated disorders (connective tissue disease, systemic autoimmune diseases, malignancy). The pathogenesis of juvenile and adult DM is presumably similar but there are important differences in some of the clinical manifestations, associated disorders, and outcomes. In this study, we investigated the clinical characteristics and outcomes of 16 patients with juvenile DM and 48 with adult DM. This study recognizes distinctive characteristics of juvenile DM such as higher frequency of neck muscle involvement, subcutaneous calcifications, and better outcomes.

A novel GDAP1 Q218E mutation in autosomal dominant Charcot-Marie-Tooth disease.

A wide range of phenotypes have been reported in autosomal recessive (AR) Charcot-Marie-Tooth disease (CMT) patients carrying mutations in the ganglioside-induced differentiation-associated protein 1 (GDAP1) gene, such as axonal, demyelinating, and intermediate forms of AR CMT. There have been very few reports of GDAP1 mutations in autosomal dominant (AD) CMT. Here, we report an AD CMT family with a novel Q218E mutation in the GDAP1 gene. The mutation was located within the well-conserved glutathione S-transferase (GST) core region and co-segregated with the affected members in the pedigree. The affected AD CMT individuals had a later disease onset and much milder phenotypes than the AR CMT patients, and the histopathologic examination revealed both axonal degeneration and demyelination.