Decreased procoagulant phospholipids in patients treated by vitamin K antagonists

Introduction

The stimulation of cells by thrombin is associated with the release of microparticles (MPs) from cell membranes. These MPs can express procoagulant activity. As vitamin K antagonists (VKA) decrease the generation of thrombin, we compared plasma procoagulant phospholipids (PPL) levels in patients with a previous history of venous thrombosis who were being treated with VKA and compared them with an untreated group.

Materials and methods

Plasma PPL were measured using a factor Xa-based coagulation assay. sGPV, a marker of platelet activation by thrombin, was measured by ELISA. Platelet MPs were also evaluated using standard flow cytometric techniques. Ninety-six VKA-treated patients and 80 patients not undergoing VKA therapy were tested and the results compared.

Results

PPL activity was significantly reduced (p < 0.0001) in VKA-treated patients compared with the untreated group. PPL were correlated with platelet and white blood cell count and with sGPV levels in the untreated group, but not in VKA-treated patients. PPL were correlated with fibrinogen levels in both groups, but not with C-reactive protein. Polymorphonuclear neutrophils (PMN) were significantly lower (p = 0.01) in VKA-treated patients than in untreated patients.

Conclusion

The difference between PPL levels in VKA-treated patients and patients without treatment could be related to the decrease in PMN count. It remains to be established if this decrease of PPL is directly related to the capacity of activated PMN to generate MPs, or indirectly by reducing the amount of pro-inflammatory cytokines or reactive oxygen species produced by PMN.     

Copy number variation upstream of PMP22 in Charcot�CMarie�CTooth disease

In several individuals with a Charcot–Marie–Tooth (CMT) phenotype, we found a copy number variation (CNV) on chromosome 17p12 in the direct vicinity of the peripheral myelin protein 22 (PMP22) gene. The exact borders and size of this CNV were determined by Southern blot analysis, MLPA, vectorette PCR, and microarray hybridization analyses. All patients from six apparently unrelated families carried an identical 186-kb duplication different from the commonly reported 1.5-Mb duplication associated with CMT1A. This ancestral mutation that was not reported in the human structural variation database was only detected in affected individuals and family members. It was absent in 2124 control chromosomes and 40 patients with a chronic inflammatory demyelinating polyneuropathy (CIDP) and therefore should be regarded as causative for the disease. This variant escapes most routine diagnostic screens for CMT1A, because copy numbers of PMP22 probes were all normal. No indications were found for the involvement of the genes that are located within this duplication. A possible association of this duplication with a mutation in the PMP22 coding regions was also excluded. We suggest that this CNV proximal of the PMP22 gene leads to CMT through an unknown mechanism affecting PMP22 expression.     

Severe Charcot‐Marie‐Tooth disease type 1E caused by a novel p.Phe84Leufs*24 PMP22 point mutation

We report a severe phenotype of Charcot‐Marie‐Tooth (CMT) disease type 1E caused by a novel p.Phe84Leufs*24 PMP22 point mutation. Ultrastructural examination of a nerve biopsy showed non‐ or partly myelinated axons which were surrounded by “onion bulb” formations mainly composed of concentric basement membranes and characterized by the presence of prominent concentric or longitudinal collagen fibrils interspersed with basement membranes. PMP22 point mutations are rare and responsible for polyneuropathies often demyelinating with onion bulb formations composed of concentric and redundant basement membranes. Entrapment of prominent collagen fibrils within onion bulb formations is unusual, even in the large spectrum of CMT disease with long duration and severe damage.     

Mutational analysis of Greek patients with suspected hereditary neuropathy with liability to pressure palsies (HNPP): a 15‐year experience

There has been limited information from population studies regarding the overall frequency of the common 1.5‐Mb 17p11.2 deletion and even scarcer data regarding the overall frequency of PMP22 micromutations in patients with a clinical suspicion of hereditary neuropathy with liability to pressure palsies (HNPP). We have analysed 100 consecutive Greek patients referred for HNPP genetic testing over a 15‐year period to our Neurogenetics Unit in Athens, a reference centre for all regions of Greece. All patients were screened for the 1.5‐Mb deletion and a selected subgroup of deletion‐negative patients for PMP22 micromutations. Mutation‐positive and mutation‐negative patients were compared for various clinical parameters. In total, 54 mutation‐positive patients were identified. In index cases, the deletion frequency was 47.8%, and the PMP22 micromutation frequency was 2.2%. Within mutation‐positive patients, the common deletion represented 95.7% and PMP22 micromutations 4.3% of cases. Two previously reported PMP22 micromutations (c.364_365delCC and c.79‐2A>G) were detected. HNPP index cases had a 2.8–1 male‐to‐female ratio, similar to mutation‐negative patients. A typical phenotype (recurrent or isolated palsies) was present in 82.4% of symptomatic HNPP cases, significantly higher than mutation‐negative patients. Sensitivity of proposed electrophysiological diagnostic criteria for HNPP was calculated at 95.7% and specificity at 80.5%. In conclusion, the common HNPP deletion accounts for ～50% and PMP22 micromutations for ～2% of cases in a large consecutive cohort of patients with suspected HNPP. The mutational and phenotypic spectrum of HNPP is similar in the Greek population compared with other populations. Proposed electrophysiological diagnostic criteria perform satisfactorily in everyday clinical practice.     

Coexistence of a T118M PMP22 missense mutation and chromosome 17 (17p11.2‐p12) deletion

Introduction: We describe a 6‐year‐old girl with a T118M PMP22 mutation and heterozygous deletion of PMP22 on chromosome 17 (17p11.2‐p12) resulting in a severe sensorimotor polyneuropathy. Methods: This study is a case report in which the relevant mutations are described. Results: Foot pain, cavovarus feet, tibialis anterior atrophy, absent reflexes, and inability to walk were found when the patient was age 6 years. Nerve conduction studies showed evidence of a sensorimotor polyneuropathy and compressive mononeuropathies of bilateral median nerves at the wrist and ulnar nerves at the elbow. Genetic testing revealed deletion of a PMP22 allele and T118M PMP22 mutation in the remaining allele. Conclusions: The severe sensorimotor polyneuropathy and hereditary neuropathy with liability to pressure palsies (HNPP) in this patient was likely a consequence of both decreased expression of PMP22 causing features consistent with HNPP and unopposed expression of the T118M mutant form of PMP22 that is relatively benign in the heterozygous state. The T118M mutant form of PMP22 can be disease‐modifying in the appropriate circumstances. Muscle Nerve 52 : 905–908, 2015     

Genetic factors for nerve susceptibility to injuries – lessons from PMP22 deficiency

Genetic factors may be learnt from families with gene mutations that render nerve-injury sus- ceptibility even to ordinary physical activities. A typical example is hereditary neuropathy with liability to pressure palsies （HNPP）. HNPP is caused by a heterozygous deletion of PMP22 gene. PMP22 deficiency disrupts myelin junctions （such as tight junction and adherens junctions）, leading to abnormally increased myelin permeability that explains the nerve susceptibility to injury. This finding should motivate investigators to identify additional genetic factors contribut- ing to nerve vulnerability of injury.     

Mutational analysis of GJB1, MPZ, PMP22, EGR2, and LITAF/SIMPLE in Serbian Charcot-Marie-Tooth patients

We report the results of mutational analysis in the following genes: GJB1 , MPZ , PMP22 , EGR2 , and LITAF/SIMPLE in 57 Charcot-Marie-Tooth (CMT) patients of Serbian origin without the PMP22 duplication. We found 10 different mutations in 14 CMT patients: 6 mutations in GJB1 , 3 in MPZ , and 1 in PMP22 . Five of six GJB1 mutations are reported for the first time, and the most frequent one appears to be a founder mutation in the Serbian population. No mutations were found in EGR2 or LITAF . Thus, GJB1 mutation analysis should be done in patients without the PMP22 duplication and male-to-male transmission of CMT.     

Developmental immunohistochemistry of the 22 kDa peroxisomal membrane protein in the human brain

We studied immunohistochemically the 22 kDa peroxisomal membrane protein (PMP 22). In the control brain, the immunopositive neurons for PMP 22 appeared 2–3 weeks earlier than those for peroxisomal enzymes. PMP 22-immunopositive glial cells appeared at 26–27 gestational weeks, increased with gestational age, and were rarely recognized after 1 year of age. In the patients with Zellweger syndrome, PMP 22-immunoreactivity was recognized in neurons, glias, liver and kidney cells.