Effectiveness of real-time quantitative PCR compare to repeat PCR for the diagnosis of Charcot-Marie-Tooth Type 1A and hereditary neuropathy with liability to pressure palsies.

The majority of cases of Charcot-Marie-Tooth type 1A (CMT1A) and of hereditary neuropathy with a liability to pressure palsies (HNPP) are the result of heterozygosity for the duplication or deletion of peripheral myelin protein 22 gene (PMP22) on 17p11.2. Southern blots, pulsed-field gel electrophoresis (PFGE), fluorescence in situ hybridization (FISH) and polymorphic marker analysis are currently used diagnostic methods. But they are time-consuming, labor-intensive and have some significant limitations. We describe a rapid real- time quantitative PCR method for determining gene copy number for the identification of DNA duplication or deletion occurring in CMT1A or HNPP and compare the results obtained with REP-PCR. Six patients with CMT1A and 14 patients with HNPP [confirmed by Repeat (REP)-PCR], and 16 patients with suspicious CMT1A and 13 patients with suspicious HNPP [negative REP-PCR], and 15 normal controls were studied. We performed REP-PCR, which amplified a 3.6 Kb region (including a 1.7Kb recombination hotspot), using specific CMT1A-REP and real-time quantitative PCR on the LightCycler system. Using a comparative threshold cycle (Ct) method and beta -globin as a reference gene, the gene copy number of the PMP22 gene was quantified. The PMP22 duplication ratio ranged from 1.35 to 1.74, and the PMP22 deletion ratio from 0.41 to 0.53. The PMP22 ratio in normal controls ranged from 0.81 to 1.12. All 6 patients with CMT1A and 14 patients with HNPP confirmed by REP-PCR were positive by real-time quantitative PCR. Among the 16 suspicious CMT1A and 13 suspicious HNPP with negative REP-PCR, 2 and 4 samples, respectively, were positive by real-time quantitative PCR. Real-time quantitative PCR is a more sensitive and more accurate method than REP-PCR for the detection of PMP22 duplications or deletions, and it is also faster and easier than currently available methods. Therefore, we believe that the real-time quantitative method is useful for diagnosing CMT1A and HNPP.

Mutational analysis of PMP22, MPZ, GJB1, EGR2 and NEFL in Korean Charcot-Marie-Tooth neuropathy patients.

We examined CMT1A duplication of 17p11.2-p12, mutations of PMP22, MPZ (P0), GJB1 (Cx32), EGR2 and NEFL genes in 57 Korean families with patients diagnosed as having Charcot-Marie-Tooth (CMT) disease. The CMT1A duplication was present in 53.6% of 28 CMT type 1 patients. In the 42 CMT families without CMT1A duplication, 10 pathogenic mutations were found in 9 families. The 10 mutations were not detected in 105 healthy controls. Seven mutations (c.318delT (p.Ala106fs) in PMP22, c.352G>A (p.Asp118Asn), c.449-1G>T (3'-splice site), c.706A>G (p.Lys236Glu) in MPZ, c.407T>C (p.Val136Ala)[corrected], c.502T>C (p.Cys168Arg) in GJB1, and c.1001T>C (p.Leu334Pro) in NEFL) were determined to be novel. The mutation frequencies of PMP22 and MPZ were similar to those found in several European populations, however, it appeared that mutations in GJB1 are less frequent in East Asian CMT patients than in Eur opean patients. We described the identified mutations and phenotype-genotype correlations based on nerve conduction studies.

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.

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.

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.