Cardiac arrest at rest and during sport activity: causes and prevention.

In the Western Countries, cardiovascular diseases are still the most frequent cause of death, which is often sudden. Sudden death (SD) in the young population occurs at a rate of 1/100 000/year and carries a profound social impact both for the young age of the victims and the unanticipated occurrence. Physical effort is a triggering risk factor, in fact SD occurs three times more frequently in athletes than in non-athletes. The screening for sport activity fitness can identify apparently healthy subjects carrying a silent abnormality able to trigger sudden cardiac death during sport activity, thus the fitness screening could be lifesaving. The spectrum of cardiovascular conditions identified at post-mortem examination is quite extensive, and include: coronary, myocardial, valvular diseases, as well as conduction system abnormalities. In 20% of the cases, the heart is normal, and sudden cardiac death is ascribed to ionic channel disease. The diagnosis of cardiomyopathy is possible with the integration of electrocardiogram and echography, thus decreasing significantly the occurrence of SD of athletes in Italy, but early diagnosis of coronary artery disease still remains challenging. The best strategy to further decrease sudden cardiac death during sport activities consists in combining early diagnosis with widespread availability of defibrillators on site.

Long-term efficacy and safety of tailored immunosuppressive therapy in immune-mediated biopsy-proven myocarditis: A propensity-weighted study.

AIMS: Standardized immunosuppressive therapy (IS) had been previously investigated in biopsy-proven (BP) lymphocytic myocarditis with heart failure (HF). This study evaluated efficacy and safety of tailored IS in BP immune-mediated myocarditis, irrespective of histology and clinical presentation. METHODS AND RESULTS: Consecutive BP myocarditis patients treated with long-term tailored IS on top of optimal medical therapy (OMT), were compared with OMT non-IS controls using propensity-score weighting. The primary outcome was a composite of death or heart transplant, the secondary outcome was a composite of biventricular function, New York Heart Association (NYHA) class variation, and relapse. IS was managed by a multidisciplinary Cardioimmunology Team, involved a safety checklist and active patients' education. Ninety-one IS patients were compared with 267 non-IS patients. IS patients more frequently had systemic immune-mediated diseases (35% vs. 9.7%), lower baseline echocardiographic left ventricular ejection fraction (35% vs. 43%), lower right ventricular fractional area change (34% vs. 41%) and higher frequency of active lymphocytic, eosinophilic and giant cell myocarditis (71% vs. 58%, 12% vs. 1.1%, and 6.6% vs. 1.5%, respectively). At 5-year follow up, no difference was observed in the primary outcome (survival rate 93% in IS vs. 87% in non-IS), but IS patients had a higher relapse rate. Thus, IS patients, with a lower biventricular function and a higher risk profile at baseline, presented similar biventricular function and NYHA class to non-IS patients at follow-up. Minor adverse drug reactions occurred in 13% of patients, all resolved with therapy switch. CONCLUSIONS: Prolonged tailored IS is effective and safe in BP immune-mediated myocarditis irrespective of histology and clinical presentation.

Classification and histological, immunohistochemical, and molecular diagnosis of inflammatory myocardial disease.

In the WHO 1996 classification of cardiomyopathies, myocarditis is defined as an "inflammatory disease of the myocardium associated with cardiac dysfunction" and is listed among "specific cardiomyopathies". Myocarditis is diagnosed on endomyocardial biopsy (EMB) by established histological, immunological, and immunohistochemical criteria, and molecular techniques are recommended to identify viral etiology. Infectious, autoimmune, and idiopathic forms of inflammatory cardiomyopathy are recognized that may lead to dilated cardiomyopathy. According to Dallas criteria, myocarditis is diagnosed in the setting of an "inflammatory infiltrate of the myocardium with necrosis and/or degeneration of adjacent myocytes, not typical of ischemic damage associated with coronary artery disease". The majority of experts in the field agree that an actual increase in sensitivity of EMB has now been reached by using immunohistochemistry together with histology. A value of >14 leukocytes/mm(2) with the presence of T lymphocytes >7 cells/mm(2) has been considered a realistic cut off to reach a diagnosis of myocarditis. The development of molecular biological techniques, particularly amplification methods like polymerase chain reaction (PCR) or nested-PCR, allows the detection of low copy viral genomes even from an extremely small amount of tissue such as in EMB specimens. Positive PCR results obtained on EMB should always be accompanied by a parallel investigation on blood samples collected at the time of the EMB. According to the recent Association for European Cardiovascular Pathology guidelines, optimal specimen procurement and triage indicates at least three, preferably four, EMB fragments, each 1-2 mm in size, that should immediately be fixed in 10 % buffered formalin at room temperature for light microscopic examination. In expected focal myocardial lesions, additional sampling is recommended. Moreover, one or two specimens should be snap-frozen in liquid nitrogen and stored at -80 °C or alternatively stored in RNA-later for possible molecular tests or specific stains. A sample of peripheral blood (5-10 ml) in EDTA or citrate from patients with suspected myocarditis allows molecular testing for the same viral genomes sought in the myocardial tissue.

Severe Fatal Mucormycosis in a Patient with Chronic Lymphocytic Leukaemia Treated with Zanubrutinib: A Case Report and Review of the Literature.

Severe mucormycosis is a fatal disease rarely complicating chronic lymphoproliferative disorders. We present a fulminant and fatal case of a 74-year-old Caucasian woman suffering from CLL treated with second-generation BTK inhibitor zanubrutinib. After a first septic episode a month prior, originating from the lung with later systemic involvement by an unidentified agent and treated with large-spectrum antibiotics and fluconazonle, a slow-onset enlarging tender warm and erythematous nodular swollen cutaneous lesion appeared in her lower limbs and spread subsequently to her upper limbs, progressing towards central ulceration with a necrotic core. Suspecting a mycotic dissemination from an unknown agent, a skin punch biopsy was performed, and intraconazole was started. Due to spread of the skin lesions, the patient was hospitalized and intravenous liposomal ampthotericin B was started. Histopathology showed an atypical sporangium-rich mycotic angioinvasion of the small vessels. Only the increase of BDG and GM could corroborate the hypothesis of mycotic infection. However, long-term CLL, immunosuppressive therapies, neutropenia, and prior use of azoles and other antimycotic agents were risk factors for mucormycosis; BTK inhibitor could also be added as another novel risk factor. Despite all therapeutic efforts, the patient died. Post-mortem molecular exams confirmed the diagnosis of disseminated mucormycosis.

Detection of SARS-CoV-2 viral proteins and genomic sequences in human brainstem nuclei.

Neurological manifestations are common in COVID-19, the disease caused by SARS-CoV-2. Despite reports of SARS-CoV-2 detection in the brain and cerebrospinal fluid of COVID-19 patients, it is still unclear whether the virus can infect the central nervous system, and which neuropathological alterations can be ascribed to viral tropism, rather than immune-mediated mechanisms. Here, we assess neuropathological alterations in 24 COVID-19 patients and 18 matched controls who died due to pneumonia/respiratory failure. Aside from a wide spectrum of neuropathological alterations, SARS-CoV-2-immunoreactive neurons were detected in the dorsal medulla and in the substantia nigra of five COVID-19 subjects. Viral RNA was also detected by real-time RT-PCR. Quantification of reactive microglia revealed an anatomically segregated pattern of inflammation within affected brainstem regions, and was higher when compared to controls. While the results of this study support the neuroinvasive potential of SARS-CoV-2 and characterize the role of brainstem inflammation in COVID-19, its potential implications for neurodegeneration, especially in Parkinson's disease, require further investigations.

Clinical profiling and outcomes of viral myocarditis manifesting with ventricular arrhythmias.

Aims: Clinical features and risk stratification of patients with viral myocarditis (VM) complicated by ventricular arrhythmias (VA) are incompletely understood. We aim to describe arrhythmia patterns and outcomes in patients with VM and early-onset VA. Methods and results: We present a single-centre study, enrolling patients with VM proven by endomyocardial biopsy, and evidence of VA within 24 h of hospitalization. The incidence of major adverse events (MAE), including all-cause death, severe heart failure, advanced atrioventricular blocks, or major VA, was evaluated during a 24-month follow-up (FU) and compared with a matched group of virus-negative myocarditis. Of patients with VM (n = 74, mean age 47 ± 16 years, 66% males, and left ventricular ejection fraction 51 ± 13%), 20 (27%) presented with major VA [ventricular tachycardia/ventricular fibrillation (VT/VF)], and 32 (44%) had polymorphic VA. Patients with polymorphic VA more commonly had evidence of ongoing systemic infection (24/32 vs. 10/42, P = 0.004) and experienced greater occurrence of MAE at discharge (15/32 vs. 2/42, P < 0.001). However, the incidence of MAE during FU was higher in patients with monomorphic VA compared to those with polymorphic VA (17/42 vs. 2/28, P = 0.002). Patients with monomorphic VA displayed frequently signs of chronic cardiomyopathy and had outcomes comparable with virus-negative myocarditis (log rank P = 0.929). Presentation with VT/VF was independently associated with MAE [at discharge: hazard ratio (HR) 4.7, 95% confidence interval (CI) 1.6-14.0, P = 0.005; during FU: HR 6.3, 95% CI 2.3-17.6, P < 0.001]. Conclusion: In patients with VM, polymorphic VA point to ongoing systemic infection and early adverse outcomes, whereas monomorphic VA suggest chronic cardiomyopathy and greater incidence of MAE during FU. Presentation with VT/VF is independently associated with MAE.

Predictors of relapse, death or heart transplantation in myocarditis before the introduction of immunosuppression: negative prognostic impact of female gender, fulminant onset, lower ejection fraction and serum autoantibodies.

AIMS: Outcome predictors in myocarditis are not well defined; we aimed at identifying predictors of death, heart transplantation (HTx) and relapse before the introduction of immunosuppression. METHODS AND RESULTS: From 1992 to 2012, 466 consecutive patients (68% male, mean age 37 ± 17 years, single centre recruitment, median follow-up 50 months) were included, of whom 216 had clinically suspected and 250 biopsy-proven myocarditis. Serum anti-heart (AHA) and anti-intercalated disk (AIDA) autoantibodies were measured by indirect immunofluorescence. Univariable and multivariable analyses of clinical and diagnostic features at diagnosis were performed. Survival free from death or HTx at 10 years was 83% in the whole study population and was lower in biopsy-proven versus clinically suspected myocarditis (76% vs. 94%, p < 0.001). Female gender (hazard ratio [HR] 2.7, 95% confidence interval [CI] 1.1-6.5), fulminant presentation (HR 13.77, 95% CI 9.7-261.73), high-titre organ-specific AHA (HR 4.2, 95% CI 1.2-14.7) and anti-nuclear antibodies (ANA) (HR 5.2, 95% CI 2.1-12.8) were independent predictors of death or HTx; higher echocardiographic left ventricular ejection fraction (LVEF) at diagnosis was protective, with a 0.93-fold risk reduction for each 1% LVEF increase (95% CI 0.89-0.96). History of myocarditis at diagnosis (HR 8.5, 95% CI 3.5-20.7) was an independent predictor of myocarditis relapse at follow-up; older age was protective (HR 0.95, 95% CI 0.91-0.99). Predictors of death, HTx and relapse did not differ in biopsy-proven versus clinically suspected myocarditis. CONCLUSIONS: Young age and a previous myocarditis were independent relapse predictors; female gender, fulminant onset, lower LVEF at presentation and high-titre organ-specific AHA and ANA were independent predictors of death and HTx, suggesting that autoimmune features predict worse prognosis.

Sudden cardiac death, borderline myocarditis and molecular diagnosis: evidence or assumption?

PURPOSE: Sudden unexpected death autopsy is sometimes non-conclusive both from a macroscopic and from a histological point of view, even if carried out according to the guidelines for sudden cardiac death examination. Molecular biology techniques are required in this setting and may play a crucial role in reaching the final diagnosis. A CASE REPORT: The postmortem examination and toxicology findings of the body of a young monk found dead in his cell were negative. Rare focal myocardial lymphocytic infiltrates were seen microscopically, associated with interstitial oedema. The findings were not sufficient to diagnose a myocarditis as the certain final cause of cardiac arrest. According to the recent guidelines for sudden cardiac death, a molecular investigation by polymerase chain reaction analysis was performed on samples of myocardium and spleen, with detection of parvovirus B19 DNA in the myocardium. Accordingly, a diagnosis of parvovirus B19 borderline acute myocarditis was put forward as the possible cause of sudden cardiac death. CONCLUSION: In sudden death cases in which there is lack of a cause-effect relationship with the postmortem findings, the final report should be expressed as a descriptive association of evidence, not providing unreliable certainty, as the Association for European Cardiovascular Pathology recommends.

A rare cause of effusive-constrictive pericarditis.

Effusive-constrictive pericarditis (ECP) is an uncommon diagnosis, frequently missed due to its heterogeneous presentation, but a potentially reversible cause of heart failure. A 62-year-old Caucasian male presented with remittent right heart failure and mild-moderate pericardial effusion. Following an initial diagnosis of idiopathic pericarditis, indomethacin was started, but the patient shortly relapsed, presenting with severe pericardial effusion and signs of cardiac tamponade, requiring pericardiocentesis. ECP was diagnosed on cardiac catheterization. Cardiac computed tomography showed non-calcified, mildly thickened and inflamed parietal pericardium. Pericardiectomy was performed with symptoms remission. On histological examination of pericardium, chronic non-necrotizing granulomatous inflammation was noted. Polymerase chain reaction assay was positive for non-tuberculous mycobacteria. This case represents a rare finding of ECP with unusual presentation due to atypical mycobacteriosis in a non-immunocompromised patient and in a non-endemic area. Pericardiectomy can be an effective option in cases unresponsive to anti-inflammatory treatment, even in the absence of significant pericardial thickening or calcification.

A standardized postmortem protocol to assess the real burden of sudden infant death syndrome.

Sudden unexpected infant death (SUID) is a major cause of death in infants < 1 year of age. Sudden infant death syndrome (SIDS) is a SUID still unexplained after post-mortem examination. In 2014, a protocol of post-mortem investigation was introduced to assess both the prevalence and the etiopathogenesis of SUID. Our aim was to compare SUID data before and after the application of a standardized autopsy protocol of investigation. In the time interval 2004-2018, SUID cases occurring in the Veneto Region, North-East Italy, were referred to our Core Lab. Since 2014, a complete autopsy was performed, including gross and histological study with toxicologic and molecular analysis carried out at the referral center. A total of 36 SUIDs (22 M, mean age 95.5 ± 80 days), 17 before (group A) and 19 after (group B) 2014, were collected. In group A, only 1 (6%) resulted as explained SUID, due to lymphocytic myocarditis and 16 (94%) were SIDS. In group B, 8 were SIDS (42%) and 11 (58%) explained SUID cases (p < 0.01), consisting of interstitial pneumonia and bronchiolitis in 9 and lymphocytic myocarditis in 2 cases. Molecular analysis was positive for viruses in 8 of them (73%). In conclusion, since the application of a standardized protocol of post-mortem investigation, inflammatory, mostly infective, cardio-pulmonary diseases have been identified as the most common cause of SUID, with SIDS falling from 94 to 42% of SUID. Efforts must be made to implement a uniform autopsy protocol to provide reliable epidemiological data on SIDS.

Story telling of myocarditis.

Myocarditis was discovered as heart disease at autopsy with the use of microscope. In 1900, with the name of acute interstitial myocarditis, Carl Ludwig Alfred Fiedler first reported the history of a sudden cardiac heart failure, in the absence of coronary, valve, pericardial disease or classical specific infections with multiorgan involvement. He postulated a peculiar isolated acute inflammation of the myocardium with poor prognosis due to invisible microorganisms, which years later would have been identified as viruses. Subsequent revision of Fiedler original histologic slides by Schmorl showed cases with either lymphocytic or giant cell infiltrates. The in vivo diagnosis became possible with the right heart catheterism and endomyocardial biopsy. Employment of immunohistochemistry and molecular techniques improved the diagnosis and etiology identification. The mechanism of myocyte injury by coxsackie virus was identified in protease 2A coded by the virus and disrupting the dystrophin in the cytoskeleton. Both RNA and DNA viruses may be cardiotropic, and coxsackie and adenovirus share a common receptor (CAR). Unfortunately, vaccination is not yet available. Cardiac Magnetic Resonance is a revolutionary diagnostic tool by detecting edema, of myocardial inflammation. However endomyocardial biopsy remains the gold standard for etiological and histotype diagnosis, with limited sensitivity due to sampling error. Viral lymphocytic fulminant myocarditis may not be fatal and the employment of mechanical assistant device - ECMO in acute phase for temporary support may be lifesaving with good prognosis.

Update on cardiomyopathies and sudden cardiac death.

Sudden cardiac death (SCD) remains a leading mode of death in western countries. Since SCD can be the first and last clinical presentation of the underlying disease, autopsy could be the only medical examination available for early diagnosis and it should be performed according to the guidelines of the Association for European Cardiovascular Pathology. Although the vast majority of SCD are due to coronary artery disease, non-ischemic causes of SCD do exist and are prevalent in young people with structural (i.e. arrhythmogenic, hypertrophic and inflammatory cardiomyopathy) and non-structural (ion channel diseases) cardiomyopathies, accounting for up to one half of cases. A standardized autopsy protocol, in combination with blood sampling to ensure feasibility of postmortem molecular testing if needed, is mandatory. The pathologist is called to provide the correct diagnosis and to advice the relatives on the need of a cascade clinical and genetic screening in the presence of a heredo-familial disease.

Postmortem genetic testing for conventional autopsy-negative sudden unexplained death: an evaluation of different DNA extraction protocols and the feasibility of mutational analysis from archival paraffin-embedded heart tissue.

One third of autopsy-negative sudden unexplained deaths (SUDs) can be attributed to a cardiac channelopathy. Typically, paraffin-embedded tissue (PET) is the only source of DNA available for genetic analyses. We examined different DNA extraction procedures, involving 2 deparaffinization methods, 2 digestion methods, 4 laboratory-based purification methods, and 5 commercial kits. Mutational analysis involving 25 RYR2 exons was performed on PET DNA from 35 SUD cases to evaluate the feasibility of using PET DNA for genetic testing. With the best PET-DNA extraction method, an average of only two thirds of the region of interest could be evaluated. Although we initially identified 5 missense mutations in 5 of 35 SUD cases, repeated analysis failed to confirm these mutations. DNA from PET should be considered error prone and unreliable in comprehensive surveillance of SUD-associated genes. Given these shortcomings, the standard autopsy for SUD should include archiving EDTA-preserved blood or frozen tissue to facilitate postmortem genetic testing.

Endomyocardial fibrosis: pathological and molecular findings of surgically resected ventricular endomyocardium.

Endomyocardial fibrosis (EMF) is a restrictive cardiomyopathy of unknown etiology prevalent in tropical regions affecting the inflow tract and apex of one or both ventricles, which show fibrous thickening of the endocardium and adjacent myocardium. Surgical treatment is recommended for patients in functional classes III or IV (New York Heart Association). The gross and histological features of the heart have been comprehensively studied in autopsies, but studies in surgical samples are still lacking. Histological and immunohistochemical features of EMF in surgical samples collected from 32 patients were described and correlated with clinical data. Polymerase chain reaction (PCR) and reverse transcription-PCR, performed on formalin fixed endomyocardial samples, were used retrospectively to detect genomes of certain cardiotropic viruses and Toxoplasma gondii. Ventricular endocardium was thickened by superficial acellular hyaline collagen fibers type I and III, with predominance of the former type. Besides fibrosis, a chronic inflammatory process and an anomalous lymphatic rich vascular pattern were observed in the deep endocardium, connected to the terminal coronary circulation of the myocardium, which might be an important pathological finding concerning EMF pathogenesis. Molecular analysis of the endomyocardium revealed high incidence of cardiotropic infective agents (6/12, 50%); however, their role in the disease pathogenesis is still controversial.

Viral detection and tumor necrosis factor alpha profile in tracheal aspirates from children with suspicion of myocarditis.

Pediatric myocarditis is a serious disease resulting in significant morbidity and mortality. Tracheal aspirate (TA) has been demonstrated to be a sensitive diagnostic tool to detect viral agents responsible for respiratory disorders and myocardial dysfunction. Tumor necrosis factor alpha (TNFalpha) is thought to play an important role in the pathogenesis of these disorders. The aim of the present study was to investigate the presence of different viruses and the expression of TNFalpha in children with clinical suspicion of myocarditis. Forty-five TAs from children (20 males/25 females, mean age 4.4+/-5.0 y) with myocardial dysfunction and respiratory symptoms were analyzed for detection of viral genomes by using molecular techniques. In 10 cases endomyocardial biopsy was also performed due to a severe and rapid progression of heart failure. TNFalpha mRNAs of TA and TNFalpha protein plasma levels were quantified. Viral etiology was detected in 25/45 (56%) cases: the most frequent etiology was enterovirus (19 cases, 59%). Polymerase chain reaction viral concordance was found in TA and endomyocardial biopsy. TNFalpha mRNA and TNFalpha serum levels were significantly more expressed in viral cases than nonviral cases (1.26+/-0.76 vs. 0.56+/-0.76, P=0.001). More impaired cardiac function (particularly ejection fraction) was detected in viral positive than in viral negative cases (39.91+/-20.09 vs. 55.61+/-20.36, P=0.04). TA seems to be an excellent tool for viral investigation in pediatric patients with suspicion of myocarditis. The analysis of TNFalpha in TA may represent an important marker to better define patient status.

A mechanism for sudden infant death syndrome (SIDS): stress-induced leak via ryanodine receptors.

BACKGROUND: Sudden infant death syndrome (SIDS) is the leading cause of postneonatal mortality in the United States. Mutations in the RyR2-encoded cardiac ryanodine receptor cause the highly lethal catecholaminergic polymorphic ventricular tachycardia (CPVT1) in the young. OBJECTIVE: The purpose of this study was to determine the spectrum and prevalence of RyR2 mutations in a large cohort of SIDS cases. METHODS: Using polymerase chain reaction, denaturing high performance liquid chromatography, and direct DNA sequencing, a targeted mutational analysis of RyR2 was performed on genomic DNA isolated from frozen necropsy tissue on 134 unrelated cases of SIDS (57 females, 77 males; 83 white, 50 black, 1 Hispanic; average age = 2.7 months). RyR2 mutations were engineered by site-directed mutagenesis, heterologously expressed in HEK293 cells, and functionally characterized using single-channel recordings in planar lipid bilayers. RESULTS: Overall, two distinct and novel RyR2 mutations were identified in two cases of SIDS. A 6-month-old black female hosted an R2267H missense mutation, and a 4-week-old white female infant harbored a S4565R mutation. Both nonconservative amino acid substitutions were absent in 400 reference alleles, involved conserved residues, and were localized to key functionally significant domains. Under conditions that simulate stress [Protein Kinase A (PKA) phosphorylation] during diastole (low activating [Ca2+]), SIDS-associated RyR2 mutant channels displayed a significant gain-of-function phenotype consistent with the functional effect of previously characterized CPVT-associated RyR2 mutations. CONCLUSIONS: Here we report a novel pathogenic mechanism for SIDS, whereby SIDS-linked RyR2 mutations alter the response of the channels to sympathetic nervous system stimulation such that during stress the channels become "leaky" and thus potentially trigger fatal cardiac arrhythmias.

Myocarditis and dilated cardiomyopathy in athletes: diagnosis, management, and recommendations for sport activity.

This article focuses on uncommon heart diseases associated with an increased risk for sudden death during exercise, namely, myocarditis and dilated cardiomyopathy.

Arrhythmogenic right ventricular cardiomyopathy/dysplasia: is there a role for viruses?

Arrhythmogenic right ventricular cardiomyopathy/dysplasia (ARVC/D) is a primary heart muscle disease characterized structurally by progressive fibrofatty replacement of the right ventricle and clinically by life-threatening ventricular arrhythmias with left bundle branch block morphology. Recently, there has been a great deal of interest on ARVC/D as a cause of sudden death in young people, and it has been reported as the most common cause of exercise-related sudden death among competitive athletes in Italy. An autosomic dominant familial occurrence has been recognized, and four disease-causing genes have been recently identified in the dominant forms: ryanodinic cardiac receptor 2, desmoplakin, plakophilin 2, and transforming growth factor (TGF)-beta3. Furthermore, plakoglobin has been identified as the first gene responsible for the recessive variant of ARVC/D associated with palmoplantar keratosis and woolly hair (Naxos disease). However, although much progress has been made in molecular genetics, up to today, the pathogenesis of the disease is still unclear. The occurrence of myocyte apoptosis has been documented, suggesting that recurrent bouts of apoptosis may account for progressive atrophy of the myocardium, which is then replaced by fibrofatty tissue. Considering the frequent finding of myocarditis at histology, an inflammatory theory has been advanced, and infective mechanisms have been postulated to contribute to the onset and the progression of the disease. Cardiotropic viruses have been detected in some ARVC/D cases, and they have been proposed as possible etiologic agents. Several etiopathogenetic theories are herein presented in detail with particular attention to the inflammatory/infective one and its possible links between this and the genetic/dystrophic theories are discussed.