Deletion in the CMT1A locus on chromosome 17p11.2 in hereditary neuropathy with liability to pressure palsies

Hereditary neuropathy with liability to pressure palsies (NHPP) is an autosomal dominant disease of peripheral nerves, characterized by recurrent focal neuropathies often with an underlying asymptomatic polyneuropathy. We report the clinical, electrophysiological, and histopathological findings in three families with HNPP and confirm the presence of a deletion on chromosome 17p11.2, including all the markers known to be duplicated in Charcot-Marie-Tooth disease type 1A. This deletion appears to be the underlying molecular deficit in this disease and provides additional evidence for the importance of this locus for peripheral nerve function.     

Epidemiology of hereditary neuropathy with liability to pressure palsies (HNPP) in south western Finland

An epidemiological study of hereditary neuropathy with liability to pressure palsies (HNPP) was carried out in south western Finland, with a population of 435,000. The diagnosis was established in 69 patients from 23 unrelated families through family and medical history, clinical neurological and neurophysiological examinations and with documentation of the deletion at gene locus 17p11.2 in at least one member of each family. This gave a prevalence of at least 16/100,000, which is remarkably high. However, due to the insidious nature of HNPP, most probably it is still an underestimation. This is the first population-based prevalence figure reported for HNPP. The prevalence is somewhat lower than that obtained for CMT in the same population, which agrees with the proposal that HNPP and CMT 1A are reciprocal products of the same unequal crossing-over. The clinical pictures of our patients were, in general, similar to those previously described in HNPP.     

A case of hereditary neuropathy with liability to pressure palsies (HNPP) with diabetes mellitus

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant neuropathy recently reported to be associated with deletion of the peripheral myelin protein-22 (PMP-22) gene. We report a 39-year-old man with recurrent brachial plexopathy and foot drop complicated by uncontrolled diabetes mellitus (DM). Right foot drop occurred at 31 years of the age and the patient subsequently experienced difficulty in raising his right arm. Neurological examination revealed weakness of the right deltoid, biceps muscles and tibialis anterior muscles. Deep tendon reflexes were generally absent. Sensory nerve conduction velocities in th ulnar, median and sural nerves were prolonged. Serum glucose and HB Alc levels were elevated to 468 mg/dl and 12.5%, respectively. Initially, it was difficult to diagnose the neuropathy as HNPP because the patient had poorly controlled diabetes mellitus and was unaware of similar disease in his family. In addition, focal asymmetric motor neuropathy and good recovery can develop in diabetes mellitus, occasionally with recurrence. We were able to make a final diagnosis of HNPP by detecting deletion of the PMP-22 gene region. After the diagnosis was confirmed, we examined the patient's family and found that his father experienced recurrent episodes of bilateral foot drop. This case suggests that gene analysis is sometimes essential in the differential diagnosis of hereditary peripheral neuropathies.     

Correlation between PMP-22 messenger RNA expression and phenotype in hereditary neuropathy with liability to pressure palsies

Hereditary neuropathy with liability to pressure palsies (HNPP) is associated with a deletion in chromosome 17p11.2, which includes the gene for the peripheral myelin protein 22 (PMP-22). A "gene dosage" effect is probably the mechanism underlying HNPP, but the amount of PMP-22 mRNA in sural nerves of HNPP patients is highly variable and the role of PMP-22 underexpression in impairing myelination has yet to be clarified. We have studied 6 genetically proven HNPP patients, to evaluate the relationship between PMP-22 mRNA levels, and clinical, neurophysiological, and neuropathological findings. Underexpression of PMP-22 mRNA correlates with disease severity and with mean axon diameter and g ratio, but not with myelin thickness, number of "tomacula," or nerve conduction parameters. Our findings further confirm that underexpression of PMP-22 is the main pathogenetic mechanism underlying the severity of clinical symptoms and signs in HNPP. Smaller axons in sural nerves of HNPP patients with lower PMP-22 levels suggests that underexpression of PMP-22 may also affect axon development.     

Gene dosage effects in hereditary peripheral neuropathy. Expression of peripheral myelin protein 22 in Charcot-Marie-Tooth disease type 1A and hereditary neuropathy with liability to pressure palsies nerve biopsies

A duplication of a 1.5-Megabase genomic region encompassing the gene for the peripheral myelin protein 22 (PMP22) is found on chromosome 17p11.2-12 in Charcot-Marie-Tooth disease type 1A (CMT1A), whereas the reciprocal deletion is associated with hereditary neuropathy with liability to pressure palsies (HNPP). Since most CMT1A patients harbor three copies of the PMP22 gene, and most HNPP patients carry only a single copy, a gene dosage effect has been proposed as a mechanism for both diseases. We have analyzed the steady-state expression of PMP22 protein in sural nerve biopsies from three CMT1A and four HNPP patients. Quantitative immunohistochemical determination showed that PMP22 protein expression relative to that of myelin protein zero and myelin basic protein was increased in all CMT1A patients and reduced in all HNPP patients, as compared with biopsy samples of patients with normal PMP22 gene expression. These data demonstrate that both neuropathies result from an imbalance of PMP22 protein expression.     

Atypical hereditary neuropathy with liability to pressure palsies (HNPP): the value of direct DNA diagnosis

We report two patients with suspected hereditary liability to pressure palsies. Neurophysiological studies showed a mixed axonal-demyelinating sensory-motor polyneuropathy with focal slowing of conduction velocities at the common sites of entrapment. Morphological studies on sural nerve biopsy from the proband showed active axonal regeneration without typical tomacula. Molecular analysis confirmed the presence of a deletion of chromosome 17p11.2 in both patients. Our observation confirms the heterogeneity of hereditary liability to pressure palsies and the relevance of DNA testing for the diagnosis of this hereditary neuropathy.     

Detection of Salmonella typhi in the blood of patients with typhoid fever by polymerase chain reaction

A polymerase chain reaction (PCR)-based test was developed for the detection of Salmonella typhi in the blood specimens from patients with typhoid fever. Two pairs of oligonucleotide primers were designed to amplify a 343-bp fragment of the flagellin gene of S. typhi. Amplified products were analyzed by agarose gel electrophoresis and Southern blot hybridization by using a 32P-labeled 40-base probe internal to the amplified DNA. The nested PCR with two pairs of primers could detect 10 organisms of S. typhi as determined by serial dilutions of DNA from S. typhi. The peripheral mononuclear cells from 11 of 12 patients with typhoid fever confirmed by blood culture were positive for DNA fragment of the flagellin gene of S. typhi, whereas 10 blood specimens of patients with other febrile diseases were negative. With the nested PCR, S. typhi DNAs were detected from blood specimens of four patients with suspected typhoid fever on the basis of clinical features but with negative cultures. We suggest that the PCR technique could be used as a novel diagnostic method of typhoid fever, particularly in culture-negative cases.     

Detection of Salmonella cells within 24 to 26 hours in poultry samples with the polymerase chain reaction BAX system

The parents of 470 students randomly selected from 1321 students attending a state high school were surveyed during the 1993-94 measles epidemic, by means of a take-home questionnaire. The response rate was 87%. Thirty stated that their child had measles during this epidemic; nine of these 30 gave a history of previous vaccination. Overall, 312 of the 470 (76%) stated that their child had been vaccinated, but only 34% indicated that they had vaccination records. There were no measles cases during this epidemic in the group with records. Those not vaccinated were at 10 times increased risk of contracting measles compared to those who had been vaccinated with or without records. Vaccine efficacy estimated in general a decade after vaccination based on parental recall of vaccination status regardless of whether they had vaccination records or not was 91% (95% CI 80%-96%). This calculation excluded 123 who claimed to have had measles prior to 1993 and 30 uncertain of their vaccination status.     

A 1.5-Mb deletion in 17p11.2-p12 is frequently observed in Italian families with hereditary neuropathy with liability to pressure palsies

Hereditary neuropathy with liability to pressure palsies (HNPP) is an autosomal dominant disorder characterized by recurrent mononeuropathies. A 1.5-Mb deletion in chromosome 17p11.2-p12 has been associated with HNPP. Duplication of the same 1.5-Mb region is known to be associated with Charcot-Marie-Tooth disease type 1 (CMT1A), a more severe peripheral neuropathy characterized by symmetrically slowed nerve conduction velocity (NCV). The CMT1A duplication and HNPP deletion appear to be the reciprocal products of a recombination event involving a repeat element (CMT1A-REP) that flanks the 1.5-Mb region involved in the duplication/deletion. Patients from nine unrelated Italian families who were diagnosed with HNPP on the basis of clinical, electrophysiological, and histological evaluations were analyzed by molecular methods for DNA deletion on chromosome 17p. In all nine families, Southern analysis using a CMT1A-REP probe detected a reduced hybridization signal of a 6.0-kb EcoRI fragment mapping within the distal CMT1A-REP, indicating deletion of one copy of CMT1A-REP in these HNPP patients. Families were also typed with a polymorphic (CA)n repeat and with RFLPs corresponding to loci D17S122, D17S125, and D17S61, which all map within the deleted region. Lack of allelic transmission from affected parent to affected offspring was observed in four informative families, providing an independent indication for deletion. Furthermore, pulsed-field gel electrophoresis analysis of SacII-digested genomic DNA detected junction fragments specific to the 1.5-Mb HNPP deletion in seven of nine Italian families included in this study. These findings suggest that a 1.5-Mb deletion on 17p11.2-p12 is the most common mutation associated with HNPP.     

Detection of Mycoplasma pneumoniae by polymerase chain reaction in lung aspirates from patients with community-acquired pneumonia

STUDY OBJECTIVE: This study was designed to evaluate the usefulness of polymerase chain reaction (PCR) to detect Mycoplasma pneumoniae DNA in samples obtained by transthoracic needle aspiration (TNA). DESIGN: Prospective study of cases. SETTING: A university hospital in Lleida, Spain. PATIENTS: A total of 101 unselected patients, admitted between January 1993 and March 1994 in the emergency department, with a clinical and radiologic picture of community-acquired pneumonia, and without contraindications for TNA application. INTERVENTIONS: Patients were studied with conventional diagnostic techniques for community-acquired pneumonia. In addition, a sample obtained by TNA was processed by the following methods: culture in standard media, culture in selective media for Legionella, detection of capsular antigens for Streptococcus pneumoniae and Haemophilus influenzae, and detection of M pneumoniae specific genome by PCR. RESULTS: Serologic data were not available in eight patients and were excluded from this analysis. M pneumoniae PCR amplification was possible in eight cases, well correlated with serologic responses indicating current infection. Samples from ten additional patients, negative by PCR, were found to be demonstrative of recent M pneumoniae infection by serologic study. Finally, in all the remaining 75 cases, including the 59 patients for whom a different microbial diagnosis was established, M pneumoniae PCR test gave negative results. CONCLUSION: This study indicates that PCR, applied to samples obtained by TNA, appears to be a moderately sensitive and highly specific method for rapid detection of M pneumoniae lung infection.     

Detection of Salmonella enteritidis in eggs by the polymerase chain reaction

A polymerase chain reaction (PCR) for the specific detection of the gene sequence, sefA, encoded by all isolates of Salmonella enteritidis, was developed. The PCR could detect as few as four S enteritidis washed bacterial cells but egg contents inhibited the PCR. Eggs spiked with 50 S enteritidis bacterial cells were homogenised, inoculated into buffered peptone water and grown at 37 degrees C for 16 hours, when the PCR was successful. A positive internal control was developed to differentiate between true and false negative PCR results for the detection of S enteritidis. In a limited trial of the egg handling procedures and the PCR, one of 250 chickens' eggs from retail outlets was found to be contaminated with S enteritidis.     

Detection of Leishmania DNA by polymerase chain reaction in scars of treated human patients

Leishmaniasis is an endemic disease in developing countries. The efficacy of therapy is usually evaluated through clinical parameters. To define the parasitologic cure, 20 patients were biopsied before and 1 month to 8 years after treatment. Paraffin-embedded tissue was used for DNA isolation. All patients had a positive polymerase chain reaction (PCR) result before therapy, except 1, for whom no histopathologic material was available. The causative agent was identified as belonging to the Leishmania (Viannia) subgenus by hybridization. Despite clinical healing and absence of reactivation or development of mucosal lesions, PCR was positive in scars of 16 patients (80%). The results suggest that parasites persist in the skin for many years despite treatment. Depending on specific pathogenetic features of the parasite and the immune status of the host, this phenomenon might result in mucosal lesions. Alternatively, it could have a role in the maintenance of immunologic memory in patients living in areas in which leishmaniasis is endemic.     

Autosomal dominant Charcot-Marie-Tooth disease type 1A and hereditary neuropathy with liability to pressure palsies: detection of the recombination in Slovene patients and exclusion of the potentially recessive Thr118Met PMP22 point mutation

Charcot-Marie-Tooth disease type 1 (CMT1) and hereditary neuropathy with liability to pressure palsies (HNPP) are the most frequent autosomal dominantly inherited disorders of the peripheral nervous system. The recessive inheritance is observed only exceptionally. Unequal crossing-over of misaligned flanking CMT1A-REP elements on chromosome 17p11.2 is the most frequent cause of the CMT1A duplication and of the reciprocal deletion in HNPP patients. Recently a recombination was noted. In our study 71 Slovene CMT1 patients from 36 families, 12 HNPP patients from 6 families and their 31 healthy relatives were analysed for the presence of these recombination mutations. In 29 of 36 unrelated CMT1 (81%) and in all 6 unrelated HNPP patients the duplication or the deletion, on chromosome 17p11.2-12 was detected. In 26 out of 29 duplication patients (CMT1A) (90%) a 3.2 kb EcoRI/SacI duplication junction fragment was observed. The analogous 7.8 kb EcoRI/EcoRI deletion junction fragment was found in 4 out of 6 unrelated HNPP deletion patients (67%). Overall we found a recombination mutation inside the in 86% of unrelated Slovene CMT1A and HNPP patients. One hundred and thirty-six DNA samples of the CMT1 and HNPP patients and of the healthy controls were negative for the potentially recessive Thr118Met PMP22 amino acid substitution. Dominantly inherited CMT1A duplications and HNPP deletions on chromosome 17p11.2 are thus, as in most other European countries, the most common mutations in Slovene CMT1 and HNPP patients. No signs of polymorphism or of potentially recessive mutation were found at the specific Thr118Met PMP22 site.     

Species identification of intestinal microsporidiosis in HIV-positive patients using the polymerase chain reaction

BACKGROUND: Microsporidia are opportunistic parasites which, due to their morphologic characteristics, continue presenting diagnostic problems. Species-specific identification of microsporidia has become important because of varying levels of response to albendazole, which is the only effective treatment for some kinds of intestinal microsporidiosis. Although these parasites cause up to 50% of otherwise unexplained chronic diarrhea in HIV-positive patients, the number of reported cases is still very scarce in our country when compared to the existing HIV-positive population. METHODS: Intestinal microsporidiosis in HIV-positive patients with diarrhea was investigated using the modified trichrome staining technique. Microsporidia species identification was done by indirect immunofluorescence (IIF) and polymerase chain reaction (PCR) with specific primers. RESULTS: Six new cases of intestinal microsporidiosis caused by Enterocytozoon bieneusi were diagnosed in Madrid (Spain). All patients were in an advanced state of the HIV infection and they presented CD4+ values equal or inferior to 100 x 10(6)/I. CONCLUSIONS: Due to the number of cases that are accumulating, microsporidia must be included among the enteropathogens responsible for chronic diarrhea in HIV-positive individuals in Spain. The PCR technique using specific primers is a suitable determinator of the microsporidia species implicated in this intestinal pathology.     

Diagnosis of mycotic infections in oncology patients using the polymerase chain reaction]

Diagnosis of mycotic infections is despite the immense effort devoted to this problem still very inaccurate. A new and promising method is the polymerase chain reaction, PCR, which theoretically can detect a single cell. In their original study the authors decided to develop a new method for the detection of fungi by PCR and to compare this examination with post-mortem findings. Thus it was possible to determine sufficiently reliably the sensitivity and specificity of the method. For the detection of fungi the authors selected the sequence coding for a small subunit of ribosomal RNA (18S rDNA). The method is able to detect the amount of DNA from some 10-100 cells. The sensitivity was 90% and the specificity 92%. The method is so far too laborious for common practice, its simplification would be however very useful.     

Serological diagnosis of hepatitis C virus in patients with liver disease in Saudi Arabia. Evaluation of antibody determination by recombinant immunoblot assays in relation to RNA detection by polymerase chain reaction

Sera from 164 Saudi Arabian patients with non-A, non-B hepatitis liver disease were examined for antibodies to hepatitis C virus (HCV) by second- and third-generation recombinant immunoblot assay (RIBA-2 and RIBA-3) and for HCV RNA by polymerase chain reaction (PCR). By using RIBA-2, 92 (56.1%) were reactive, 64 (39%) were nonreactive, and 8 (4.9%) were indeterminate. By using RIBA-3, 98 (59.7%) were reactive 60 (36.6%) were nonreactive, and 6 (3.7%) were indeterminate. By using PCR, 108 (65.9%) were positive. Of the eight RIBA-2 indeterminate samples, seven became RIBA-3 reactive but PCR-positive, and one became RIBA-3 nonreactive but PCR-negative. Of the six RIBA-3 indeterminate samples, five were RIBA-2 nonreactive but PCR-positive, and one was RIBA-2 reactive but PCR-negative. From our study on Saudi patients, we conclude that RIBA-3 has slightly but not significantly improved the results of anti-HCV antibody detection, and is probably of more value to resolve those indeterminate samples by RIBA-2. Although expensive, PCR remains the most reliable HCV diagnostic method until an HCV antigen detection test is available.     

Detection of pathogenic fungi in human blood by the polymerase chain reaction

The ability of the polymerase chain reaction (PCR) to detect pathogenic fungi in human blood was investigated. A DNA fragment of about 300 bp from the 18S rDNA, highly conserved in all fungi, was amplified with target DNA from 18 different species of fungi commonly isolated from clinical samples. The presence of PCR products was confirmed by hybridization with a fluorescein-labelled internal probe (21-mer). The PCR assay described is sensitive enough to detect 125 fg of purified Candida albicans DNA and 10 to 100 yeast cells per millilitre of blood.     

Detection of EBV in tumor tissue and peripheral blood by polymerase chain reaction in patients with nasopharyngeal carcinoma

Sixty-nine untreated patients with a pathologically verified nasopharyngeal carcinoma were selected for the study of detection of EBV in nasopharyngeal tumor and peripheral blood by polymerase chain reaction (PCR). Primers were directed to conserved regions of EBV genome encoding capsid protein gp 220 (Bam HI L region). A distinct 239 bp band of the PCR products indicated the presence of EBV. Results showed that EBV DNA was obtained in 91.3% of 69 NPC patients and 16.7% of 18 healthy individuals on nasopharyngeal tissue, and the difference was statistically significant between the above two groups. Nevertheless, no EBV DNA was verified from the mononuclear cells of the peripheral blood of the two groups. There was no relationship between the positive EBV DNA and the titer of serological markers. Meanwhile, the positive EBV DNA did not show any relationship with the histology type, tumor and nodal bulk, or even metastasis. Although a high positive rate of EBV DNA was detected in nasopharyngeal tumor of patients, additional environmental and genetic factors must still be considered.     

Diagnosis of Mycoplasma pneumoniae pneumonia in pediatric patients by polymerase chain reaction (PCR)

Polymerase chain reaction (PCR) testing was performed on respiratory tract specimens obtained by throat swab in 21 children admitted to the hospital with suspected Mycoplasma pneumoniae pneumonia. Of 13 patients with a clinical condition compatible with mycoplasma infection and an immunological response to M. pneumoniae, 11 were positive by PCR. Eight patients were negative by serology and/or had a clinical condition not compatible with mycoplasma infection, and all were negative by PCR. The antibody response to M. pneumoniae was delayed for a week or more in 3 (23%) of the 13 patients with documented mycoplasma infection. These results suggest that PCR performed on a respiratory tract specimen obtained by a throat swab may be useful in the initial evaluation of children with suspected M. pneumoniae pneumonia, especially in patients in whom the serological response is delayed.