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Biomedical subjects

M G Hanna

Publications and source records attributed to M G Hanna.

At least 19 recordsLinked to original sources
PubMed2006

POLG1, C10ORF2, and ANT1 mutations are uncommon in sporadic progressive external ophthalmoplegia with multiple mitochondrial DNA deletions.

The authors sequenced POLG1, C10ORF2, and ANT1 in 38 sporadic progressive external ophthalmoplegia patients with multiple mitochondrial DNA (mtDNA) deletions. Causative mutations were identified in approximately 10% of cases, with two unrelated individuals harboring a novel premature stop codon mutation (1356T>G). None had a mutation in C10ORF2 or ANT1. In the majority of patients, the primary nuclear genetic defect is likely to affect other unknown genes important for mtDNA maintenance.

Adenine Nucleotide Translocator 1↗
PubMed2006

Genetic association studies of complex neurological diseases.

Genetic association studies offer a powerful approach to identify the multiple variants of small effect that modulate susceptibility to common, complex disease. They, however, have a poor reputation, mainly because of the consistent lack of replication of all but a few. Thousands of genetic studies have been carried out on multifactorial diseases in the past 30 years, yielding only about 50 variants that can be considered to be true positives. Although the positive studies show proof of principle, the multitude of negative studies indicate fundamental problems in the design and execution of association studies. Here, we discuss some of the more pertinent study design and data analysis issues which can affect the outcome of genetic association studies.

Case-Control Studies↗
PubMed2005

Andersen-Tawil syndrome: new potassium channel mutations and possible phenotypic variation.

OBJECTIVE: To evaluate clinical, genetic, and electrophysiologic features of patients with Andersen-Tawil syndrome (ATS) in the United Kingdom. METHODS: Clinical and neurophysiologic evaluation was conducted of 11 families suspected to have ATS. Molecular genetic analysis of each proband was performed by direct DNA sequencing of the entire coding region of KCNJ2. Control samples were screened by direct DNA sequencing. The electrophysiologic consequences of several new mutations were studied in an oocyte expression system. RESULTS: All 11 ATS families harbored pathogenic mutations in KCNJ2 with six mutations not previously reported. Some unusual clinical features including renal tubular defect, CNS involvement, and dental and phonation abnormalities were observed. Five mutations (T75M, D78G, R82Q, L217P, and G300D) were expressed, all of which resulted in nonfunctional channels when expressed alone, and co-expression with wild-type (WT) KCNJ2 demonstrated a dominant negative effect. CONCLUSION: Six new disease-causing mutations in KCNJ2 were identified, one of which was in a PIP2 binding site. Molecular expression studies indicated that five of the mutations exerted a dominant negative effect on the wild-type allele. KCNJ2 mutations are an important cause of ATS in the UK.

Adolescent↗
PubMed2005

The primary periodic paralyses: diagnosis, pathogenesis and treatment.

Periodic paralyses (PPs) are rare inherited channelopathies that manifest as abnormal, often potassium (K)-sensitive, muscle membrane excitability leading to episodic flaccid paralysis. Hypokalaemic (HypoPP) and hyperkalaemic PP and Andersen-Tawil syndrome are genetically heterogeneous. Over the past decade mutations in genes encoding three ion channels, CACN1AS, SCN4A and KCNJ2, have been identified and account for at least 70% of the identified cases of PP and several allelic disorders. No prospective clinical studies have followed sufficiently large cohorts with characterized molecular lesions to draw precise conclusions. We summarize current knowledge of the clinical diagnosis, molecular genetics, genotype-phenotype correlations, pathophysiology and treatment in the PPs. We focus on unresolved issues including (i) Are there additional ion channel defects in cases without defined mutations? (ii) What is the mechanism for depolarization-induced weakness in Hypo PP? and finally (iii) Will detailed electrophysiological studies be able to correctly identify specific channel mutations? Understanding the pathophysiology of the potassium-sensitive PPs ought to reduce genetic complexity, allow subjects to be stratified during future clinical trials and increase the likelihood of observing true clinical effects. Ideally, therapy for the PPs will prevent attacks, avoid permanent weakness and improve quality of life. Moreover, understanding the skeletal muscle channelopathies will hopefully lead to insights into the more common central nervous system channel diseases such as migraine and epilepsy.

Animals↗
PubMed2005

Late-onset episodic ataxia type 2 due to an in-frame insertion in CACNA1A.

Episodic ataxia type 2 (EA2) is caused by calcium channel (CACNA1A) mutations and typically begins before age 20 years. The molecular basis of late-onset EA2 is unclear. The authors describe a case of late-onset EA2 associated with the first multiple-base pair insertion in CACNA1A. Molecular expression revealed evidence of impaired calcium channel function, suggesting that genetically induced reduction in calcium channel function may associate with cases of late-onset EA2.

Adult↗
PubMed2005

Immunotherapy with autologous tumor cell-BCG vaccine in patients with colon cancer: a prospective study of medical and economic benefits.

We have completed a multicenter, randomized controlled phase III clinical trial in Stages II and III colon cancer patients with active specific immunotherapy (ASI) using autologous tumor cells with an immunomodulating adjuvant bacillus Callmette-Guerin (BCG) vaccine (OncoVAX) in an adjuvant setting. In this study, patients were randomized to receive either OncoVAX therapy or no therapy after surgical resection of the primary tumor and stratified by stage of disease. Since the biologic essence of the effective tumor immunotherapy is the presence in the vaccine of a minimum number of viable, metabolically active, autologous tumor cells, the processing of the vaccine product, occurred within 48 h after surgery. Analysis of prognostic benefit in the pivotal phase III trial, with a 5.8 year median follow-up, showed that a beneficial effect of OncoVAX is statistically significant for all endpoints including recurrence-free interval, overall survival, and recurrence-free survival in Stage II colon cancer patients. Surgery alone cures approximately 65% of Stage II (Dukes B2, B3) colon cancer patients. In the remaining patients, OncoVAX in an adjuvant setting, significantly prolongs recurrence-free interval (57.1% relative risk reduction) and significantly improves 5-year overall survival and recurrence-free survival. No statistically significant prognostic benefits were achieved in Stage III (Duke's C1-C3) patients. A health economics assessment was performed on these results in Stage II colon cancer patients using disease-free survival and overall survival (for the entire intent-to-treat population). Cost-effectiveness, cost-utility and sensitivity analysis were applied with, cost of life years, recurrence-free life years and quality adjusted life years (QALYs) as the primary endpoints to this analysis. The perspective of the economic analysis was the current direct medical cost established by the health care providers. The introduction of new technologies often leads to additional costs. This report verified that the use of OncoVAX for patients with Stage II colon cancer not only has significant prognostic benefit and positive clinical outcomes, but also showed that OncoVAX therapy yields impressive health economics benefits.

Adult↗
PubMed2005

New phenotypic diversity associated with the mitochondrial tRNA(SerUCN) gene mutation.

We performed detailed clinical, histopathological, biochemical, in vitro translation and molecular genetic analysis in patients from two unrelated families harbouring the tRNA(SerUCN) 7472C-insertion mutation. Proband 1 developed a progressive neurodegenerative phenotype characterised by myoclonus, epilepsy, cerebellar ataxia and progressive hearing loss. Proband 2 had a comparatively benign phenotype characterised by isolated myopathy with exercise intolerance. Both patients had the 7472C-insertion mutation in identical proportions and they exhibited a similar muscle biochemical and histopathological phenotype. However, proband 2 also had a previously unreported homoplasmic A to C transition at nucleotide position 7472 in the tRNA(SerUCN) gene. This change lengthens further the homopolymeric C run already expanded by the 7472C-insertion. These data extend the phenotypic range associated with the 7472C-insertion to include isolated skeletal myopathy, as well as a MERRF-like phenotype.

Adolescent↗
PubMed2005

Problems with botulinum toxin treatment in mitochondrial cytopathy: case report and review of the literature.

Botulinum toxin type A (BTXA) is widely used in neurological therapeutics for a variety of indications such as dystonia, spasticity, hyperhidrosis, and hypersalivation. It is relatively contraindicated in disorders of neuromuscular transmission, in individuals with known hypersensitivity or bleeding disorders, and during pregnancy. Two patients are presented with initially undetermined multisystem neurological disorders and excessive sialorrhoea, later diagnosed as mitochondrial cytopathy, who had side effects after treatment with ultrasound guided BTXA injections. Published reports on the use of BTXA injections in hypersalivation of various causes are reviewed, along with the proposed mechanisms of hypersensitivity to BTXA in patients with mitochondrial cytopathies. Clinicians should be cautious when using BTXA injections in such patients because of the significant risk of side effects.

Adult↗
PubMed2005

Neurological channelopathies.

Ion channels are membrane-bound proteins that perform key functions in virtually all human cells. Such channels are critically important for the normal function of the excitable tissues of the nervous system, such as muscle and brain. Until relatively recently it was considered that dysfunction of ion channels in the nervous system would be incompatible with life. However, an increasing number of human diseases associated with dysfunctional ion channels are now recognised. Such neurological channelopathies are frequently genetically determined but may also arise through autoimmune mechanisms. In this article clinical, genetic, immunological, and electrophysiological aspects of this expanding group of neurological disorders are reviewed. Clinical situations in which a neurological channelopathy should enter into the differential diagnosis are highlighted. Some practical guidance on how to investigate and treat this complex group of disorders is also included.

Autoimmune Diseases↗
PubMed2004

Expanding the phenotype of potassium channelopathy: severe neuromyotonia and skeletal deformities without prominent Episodic Ataxia.

We report an unusual family in which the same point mutation in the voltage-gated potassium channel gene KCNA1 resulted in markedly different clinical phenotypes. The propositus presented in infancy with marked muscle stiffness, motor developmental delay, short stature, skeletal deformities, muscle hypertrophy and muscle rippling on percussion. He did not experience episodic ataxia. His mother presented some years later with typical features of Episodic Ataxia type 1 (EA1), with episodes of ataxia lasting a few minutes provoked by exercise. On examination she had myokymia, joint contractures and mild skeletal deformities. A heterozygous point mutation in the voltage-gated K(+) channel (KCNA1) gene (ACG-AGG, Thr226Arg) was found in both. We conclude that mutations in the potassium channel gene (KCNA1) can cause severe neuromyotonia resulting in marked skeletal deformities even if episodic ataxia is not prominent.

Adult↗
PubMed2004

Unusual muscle disease in HIV infected patients.

Two patients presented with proximal muscle weakness, a normal or minor elevation of creatine phosphokinase (CPK) and normal findings on electromyography. Muscle biopsy in one patient revealed CD8+ polymyositis, and in the other showed ddI induced myopathy. These cases illustrate the importance of muscle biopsy in identifying the underlying pathology in HIV infected patients with muscle weakness and little or no abnormality in laboratory investigations.

Anti-HIV Agents↗
PubMed2003

A randomized controlled study of modified cobratoxin in adrenomyeloneuropathy.

Adrenomyeloneuropathy is a peroxisomal disorder that causes demyelination, with no proven therapy. Oral modified cobratoxin was assessed in a double-blind, randomized, crossover study of eight patients. Treatment was well tolerated. There were no significant improvements with therapy. The authors do not confirm previous anecdotal reports of dramatic improvement with modified cobratoxin.

Adrenoleukodystrophy↗
PubMed2003

International consensus outcome measures for patients with idiopathic inflammatory myopathies. Development and initial validation of myositis activity and damage indices in patients with adult onset disease.

OBJECTIVE: To devise new tools to assess activity and damage in patients with idiopathic myopathies (IIM). METHODS: An international multidisciplinary consensus effort to standardize the conduct and reporting of the myositis clinical trials has been established. Two tools, known as the myositis intention to treat index (MITAX) and the myositis disease activity assessment visual analogue scale (MYOACT), have been developed to capture activity in patients with IIM. In addition, the myositis damage index (MDI) has been devised to assess the extent and severity of damage developing in different organs and systems. These measures have been reviewed by the myositis experts participating in the International Myositis Assessment and Clinical Studies (IMACS) group and have been found to have good face validity and to be comprehensive. The instruments were assessed in two real patient exercises involving patients with adult dermatomyositis and inclusion body myositis. RESULTS: The reliability of MITAX, MYOACT and MDI, measured by the intraclass correlation coefficient among the physicians, and the inter-rater reliability, as assessed by variation in the physicians' rating of patients, was fair to good for most aspects of the tools. Reliability and inter-rater agreement improved at the second exercise after the participants had completed additional training. CONCLUSIONS: The MITAX, MYOACT and MDI tools, which are now undergoing validity testing, should enhance the consistency, comprehensiveness and reliability of disease activity and damage assessment in patients with myositis.

Acute Disease↗
PubMed2003

Severe infantile hyperkalaemic periodic paralysis and paramyotonia congenita: broadening the clinical spectrum associated with the T704M mutation in SCN4A.

The authors describe an Italian kindred with nine individuals affected by hyperkalaemic periodic paralysis associated with paramyotonia congenita (hyperPP/PMC). Periodic paralysis was particularly severe, with several episodes a day lasting for hours. The onset of episodes was unusually early, beginning in the first year of life and persisting into adult life. The paralytic episodes were refractory to treatment. Patients described minimal paramyotonia, mainly of the eyelids and hands. All affected family members carried the threonine to methionine substitution at codon 704 (T704M) in exon 13 of the skeletal muscle voltage gated sodium channel gene (SCN4A). The association between T704M and the hyperPP/PMC phenotype has been only recently revealed. Nevertheless, such a severe phenotype has never been reported so far in families with either hyperPP or hyperPP/PMC. These data further broaden the clinical spectrum of T704M and support the evidence that this mutation is a common cause of hyperPP/PMC.

Adolescent↗
PubMed2002

Human T cell leukaemia virus type I associated neuromuscular disease causing respiratory failure.

Polymyositis and inclusion body myositis have rarely been described in association with human T cell leukaemia virus type I (HTLV-I) infection. Most of such patients have coexisting HTLV-I associated myelopathy (HAM). Two patients with HTLV-I infection, myopathy, and respiratory failure are described. The muscle biopsy specimen of the first patient bore the histological features of inclusion body myositis and there was no evidence of concurrent myelopathy. The second patient had HAM, and her muscle biopsy showed non-specific myopathic and neuropathic changes. Both patients developed respiratory muscle weakness over eight years after diagnosis of myopathy, leading to hypercapnic respiratory failure requiring mechanical ventilatory support. Respiratory failure as a complication of HTLV-I associated myopathy has not previously been described.

Biopsy↗