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Aim: To describe the epidemiology of biopsy-proven idiopathic inflammatory myopathies (IIM) in South Australia (SA). Methods: Cases of IIM were ascertained by review of all muscle biopsy reports from the Neuropathology Laboratory, Hanson Institute (wherein all adult muscle biopsies in SA are reported) from 1980 to 2009. Clinical correlation of these patients by review of medical records was undertaken. SA population denominator numbers were obtained from the Australian Bureau of Statistics. Results: Three hundred and fifty-two biopsy-proven cases of IIM were identified between 1980 and 2009. The overall annual incidence of IIM appeared to be rising with a mean incidence of eight cases per million population (95% CI: 7.2–8.9). This corresponded with an increasing annual incidence of inclusion body myositis (IBM) (prevalence of 50.5 cases per million population in 2009, 95% CI: 40.2–62.7). A female preponderance was noted in both dermatomyositis (DM) (F : M = 2.75 : 1.00) and polymyositis (PM) (F : M = 1.55 : 1.00) but gender distribution was almost equal in IBM (F : M = 1.1 : 1.0). Mean age at diagnosis for IBM (67.5 years) was higher than for DM (55.1 years) and PM (59.0 years). A higher proportion of DM patients reported living in urban dwellings and DM patients tended to be predominantly professionals. Conclusions: In SA there is an increasing incidence of IBM and the prevalence is one of the highest reported to date. This may reflect an increase in the number of biopsies performed, improved histological techniques or a genuine increase in incidence.

Idiopathic inflammatory myopathies (IIM) are a group of rare autoimmune disorders characterized by muscle inflammation and progressive weakness. The cause of IIM is unclear but it is believed that disease expression may be triggered by unknown factors in genetically predisposed individuals. Diagnosis is based on a combination of clinical, laboratory and electromyography findings. Muscle biopsy is the definitive diagnostic test. Research into IIM has been limited by the rarity of the disease, a somewhat insidious onset, difficulties with classification and diagnostic methods and heterogeneous study populations making cross-study evaluations difficult. This paper reviews the diagnostic and classification criteria of the IIM and examines epidemiological studies that have been performed, focusing on demographics.

Aims: The long-terms complications of immunosuppressive and anti-inflammatory treatment in idiopathic inflammatory myositis (IIM) are unknown. We sought to determine the complications of these treatments in a large cohort of patients with biopsy-proven IIM. Methods: A South Australian database for patients with biopsy-proven IIM was established. Clinical details of patients including treatment received were recorded. Results: Forty-three patients with dermatomyositis (DM), 184 with polymyositis (PM) and 117 with inclusion body myositis (IBM) were registered on the database. The prevalence of hypertension and diabetes in this population was 62% and 29%, respectively, considerably higher than the background prevalence of 9.4% and 4%, making detection of treatment-related adverse effects difficult. Hypertension and ischemic heart disease were more likely to be present prior to the diagnosis of IIM rather than following it. Hypertension and diabetes occurred more frequently following the diagnosis of myositis, in patients with DM compared with PM or IBM. Conclusions: We report a novel association of IIM with hypertension, diabetes and ischemic heart disease, indicating that a comprehensive assessment of vascular risk factors is essential in IIM.

Vidya S. Limaye, Claudine S. Bonder, Wai Y. Sun, Susan Lester, Peter J. Roberts-Thomson And Peter Blumbergs

To describe the epidemiology of biopsy-proven idiopathic inflammatory myopathies (IIM) in South Australia (SA).Cases of IIM were ascertained by review of all muscle biopsy reports from the Neuropathology Laboratory, Hanson Institute (wherein all adult muscle biopsies in SA are reported) from 1980 to 2009. Clinical correlation of these patients by review of medical records was undertaken. SA population denominator numbers were obtained from the Australian Bureau of Statistics.Three hundred and fifty-two biopsy-proven cases of IIM were identified between 1980 and 2009. The overall annual incidence of IIM appeared to be rising with a mean incidence of eight cases per million population (95% CI: 7.2-8.9). This corresponded with an increasing annual incidence of inclusion body myositis (IBM) (prevalence of 50.5 cases per million population in 2009, 95% CI: 40.2-62.7). A female preponderance was noted in both dermatomyositis (DM) (F : M = 2.75 : 1.00) and polymyositis (PM) (F : M = 1.55 : 1.00) but gender distribution was almost equal in IBM (F : M = 1.1 : 1.0). Mean age at diagnosis for IBM (67.5 years) was higher than for DM (55.1 years) and PM (59.0 years). A higher proportion of DM patients reported living in urban dwellings and DM patients tended to be predominantly professionals.In SA there is an increasing incidence of IBM and the prevalence is one of the highest reported to date. This may reflect an increase in the number of biopsies performed, improved histological techniques or a genuine increase in incidence.

Idiopathic inflammatory myopathies (IIM) are a group of rare autoimmune disorders characterized by muscle inflammation and progressive weakness. The cause of IIM is unclear but it is believed that disease expression may be triggered by unknown factors in genetically predisposed individuals. Diagnosis is based on a combination of clinical, laboratory and electromyography findings. Muscle biopsy is the definitive diagnostic test. Research into IIM has been limited by the rarity of the disease, a somewhat insidious onset, difficulties with classification and diagnostic methods and heterogeneous study populations making cross-study evaluations difficult. This paper reviews the diagnostic and classification criteria of the IIM and examines epidemiological studies that have been performed, focusing on demographics.