Renato Mantegazza

Inflammatory myopathies and systemic disorders : a review of immunopathogenetic mechanisms and clinical features

Abstract The inflammatory myopathies are a heterogeneous group of muscle diseases characterized by muscle degeneration mediated by inflammatory processes. They may be idiopathic, as in polymyositis, dermatomyositis and inclusion body myositis, or associated with systemic disorders such as malignancies, overlap syndromes, and retroviral infection. The pathogenesis of each disease is discussed together with more recent molecular and cellular immunology findings. Salient diagnostic, clinical and pharmacological features are also reviewed.

A new non-radioactive method for the screening and prenatal diagnosis of myotonic dystrophy patients.

Abstract Myotonic dystrophy (DM) is an autosomal dominant neuromuscular disease with an estimated incidence of 1 in 8000 and is the most common form of muscular dystrophy affecting adults. An unstable, untranslated part of the myotonic dystrophy protein kinase gene on the long arm of chromosome 19, composed of CTG repeats, is a genetic marker for DM. We have developed a fast non-radioactive polymerase chain reaction (PCR) procedure to detect the (CTG)n repeat expansion in DM patients and their relatives. Genomic DNA extracted from peripheral blood lymphocytes was amplified by PCR using specific primers to flank the region containing the triplets. To improve the amplification of this CG-rich region, either 10% glycerol or rTth DNA polymerase XL (extra long) was added to the reaction mixture, allowing amplification of huge expansions otherwise not polymerized by PCR. The PCR products were Southern blotted and the expansion revealed using a fluorescein-labelled (CTG)10 probe. We compared our results with those obtained in 24 patients and relatives using genomic digestion followed by radioactive Southern blot; in all cases the results overlapped. The same technique was used for prenatal diagnosis in pregnant DM mothers. We conclude that this new method is reliable for the genetic testing of DM patients.

Chapter 15 Clinical Trials in Muscle Disorders

Publisher Summary This chapter discusses clinical trials in muscle disorders. It focuses on the three main areas of muscle diseases in which clinical trials have been or are being performed: (1) autoimmune ion channel disorders, (2) inflammatory myopathies, and (3) primary hereditary myopathies. A group of autoimmune disorders shares a common pathogenesis, mediated by autoantibodies against different ion channels of motor nerve terminals. Myasthenia gravis (MG) and Lambert–Eaton myasthenic syndrome (LEMS) are because of antibodies to postsynaptic acetylcholine receptors (AChRs) and presynaptic voltage-gated calcium channels, respectively. Antibodies against voltage-gated potassium channels have been reported in acquired neuromyotonia. MG is the most commonly observed disease in this group. Its natural course has been modified by the introduction of immunosuppressive drugs and thymectomy. According to the features and severity of the disease, and due to ethical reasons, treatments available for MG have been rarely evaluated in a controlled fashion. Inflammatory myopathies (IM) encompass a heterogenous group of disorders in which clinical, histopathologic, and laboratory data define three major entities: polymyositis (PM), dermatomyositis (DM), and inclusion body myositis (IBM). Although several clinical features are shared by the different forms, pathogenetic mechanisms differ considerably among PM, DM, and IBM. Several disorders mentioned in this chapter may be subdivided into the following categories: (1) muscular dystrophies, (2) congenital myopathies, and (3) myotonic syndromes. The chapter focuses on the main diseases for which a major effort has been expended to perform clinical trials: the Xp21-linked muscular dystrophies (DMD or Becker muscular dystrophies [BMD]), facioscapulohumeral muscular dystrophy (FSHD), and myotonic dystrophy (MD).

Paraneoplastic autoimmune diseases in patients with thymic malignancies: a favorable, but not independent, prognostic factor

Thymomas and thymic carcinomas are rare epithelial tumors of thymus (TETs) associated with paraneoplastic autoimmune (PN/AI) disorders, including myasthenia gravis (MG), pure red cell aplasia, hypogammaglobulinemia, encephalitis, and acquired neuromyotonia (1,2). Patients affected by these disorders are usually screened for thymoma at diagnosis, and they frequently improve with thymoma treatment (2).

Revealing the involvement of miR-376a, miR-432 and miR-451a in infantile ascending hereditary spastic paralysis by microRNA profiling in iPSCs

Infantile-onset ascending hereditary spastic paralysis (IAHSP) is a rare, early onset, autosomal recessive motor neuron disease characterized by progressive weakness and spasticity. Several mutations in the alsin 2 gene (ALS2) have been described in IAHSP patients; however, a relevant subset of patients is ALS2 mutationnegative, and pathogenic events causing the disease are unknown. The present study aimed at better understanding the molecular mechanisms underlying motor neuron loss in IAHSP patients by identifying microRNAs (miRNAs) potentially implicated in neuronal differentiation. Using the human induced pluripotent stem cell (iPSC) technology, we developed a patient-specific in vitro cellular model and performed miRNome profiling in fibroblasts, iPSCs and iPSCs-derived neurons obtained from an ALS2 mutation-negative IAHSP patient and a healthy control. The selected differentially expressed miRNAs were also analyzed in fibroblasts, iPSCs and iPSCs-derived neurons from two patients affected by other motor neuron diseases, two patients with other neurological disease, and three healthy controls. We found that miR-376a, miR-432 and miR-451a expression was altered in cell cultures obtained from the IAHSP patient compared to the other patients and controls. In addition, the hierarchical clustering analysis revealed that miR-451a was differentially expressed in fibroblasts and iPSCs, whereas miR-376a and miR432 in neuronal cells. These results, together with the miRNA/mRNA target analysis, were indicative of a significant involvement of miR-451a in stem cell biology processes, and of miR-376a and miR-432 in the establishment of the neuronal phenotype. Our overall findings identified miR-376a, miR-432 and miR-451a as molecules involved in neuronal differentiation, and potentially in IAHSP pathogenesis, which could provide cues for future development of patient-specific miRNAbased therapeutic strategies for IAHSP or other motor neuron diseases.

Autoimmune Ion Channel Disorders of the Peripheral Nervous System

Myastenia gravis (MG) (ocular MG, generalized MG, thymoma-associated MG) is an autoimmune disorder caused by antibodies (Ab) against the motor post-synaptic acetylcholine receptors (AChRs). Mortality rate of non-paraneoplastic MG is ~ 2 %.

Idiopathic Inflammatory Myopathies: A Review of Immunopathological Features and Current Models of Pathogenesis

The idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of chronic systemic disorders characterized by muscle inflammation and progressive muscle weakness. The major clinical variants are dermatomyositis (DM) including a distinct juvenile (JDM) subtype, polymyositis (PM), and inclusion body myositis (IBM) (Engel & Hohlfeld, 2004). IBM is divided into sporadic IBM (sIBM), the most common muscle disease starting after age 50 years, occurring mainly in men and leading to severe disability, and hereditary inclusion body myopathy, characterized by pathologic alterations resembling those of sIBM except for a lack of muscle inflammation (hence “myopathy” instead of “myositis”) (Askanas & Engel, 1998). DM may occur in children or adults and is considered a humorally-mediated microangiopathy, while PM occurs mainly after the second decade of life and is a T cell-mediated disease characterized by cytotoxic attack against non-necrotic muscle fibers (Dalakas, 2011c). For all IIM forms, both target antigens and triggering factors for autoimmune response remain unknown. A growing body of evidence suggests that genetically susceptible individuals probably develop an idiopathic inflammatory myopathy in response to particular environmental stimuli (Feldman et al., 2008; Needham & Mastaglia, 2007; O’Hanlon et al., 2006; O’Hanlon & Miller, 2009; Rider et al., 2010; Sarkar et al., 2005; Vegosen et al., 2007).

Aspects of Clinical Preparation of Thymectomy in Myasthenic Cases with or without Thymoma and the Clinico-Biological Follow-up of the Thymectomized Patients

Several uncontrolled studies performed since the 1950s proved that thymectomy is effective in Myasthenia Gravis (MG). MG is an autoimmune disease characterized by muscle weakness and fatigability in which autoantibodies (AntiAChR-Ab) are targeted to the acetylcholine receptor (AChR) at the neuromuscular junction.1 Aim of surgery is to remove the site of autoantigen sensibilization and self-sustainment of the autoimmune response. Previous studies showed that the efficacy of thymectomy is positively correlated with the time from diagnosis, young age and absence of thymoma.2,3,4 Furthermore, over the last two decades there has been considerable debate on the best surgical technique in terms of tolerability and clinical outcome.5,6 Transcervical thymectomy, a relatively easy procedure with minimal postoperative morbidity,7 may fail to remove the entire gland and miss ectopic thymic tissue often present in the neck and mediastinum.8 In this regard, transsternal thymectomy is required to remove all thymic tissue and is now accepted as the technique associated with the higher remission rate in MG.9 Extended transsternal thymectomy (ETT) combines the removal of thymus and fat tissue from the pericardic and cervical regions in which functional thymic remnants may persist, usually in the space from the thyroid gland to the diaphragm, between the two phrenic nerves.10 Since the extended approach requires a median sternotomy, ETT is a major surgical procedure which may limit the indication of thymectomy in patients with bulbar or ocular MG, and in patients in which surgical morbidity may have detrimental effects on patients’ condition. Moreover, a median sternotomy is sometimes not easily accepted by female patients for aesthetical reasons.