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Ann Rheum Dis. 2015 Aug;74(8):1551-6. doi: 10.1136/annrheumdis-2013-205127. Epub 2014 Apr 2.

Prevalence and clinical characteristics of adult polymyositis and dermatomyositis; data from a large and unselected Norwegian cohort.

Author information

1
Department of Rheumatology, Oslo University Hospital, Oslo, Norway.
2
Department of Rheumatology, Sørlandets sykehus, Kristiansand, Norway.
3
Department of Rheumatology, Betanien Hospital, Skien, Norway.
4
Revmatismesykehuset, Lillehammer, Norway.
5
Department of Rheumatology, Sykehuset Østfold, Moss, Norway.
6
Department of Neurology, Sykehuset Østfold, Fredrikstad, Norway.
7
Department of Rheumatology, Oslo University Hospital, Oslo, Norway Institute of Clinical Medicine, University of Oslo, Oslo, Norway.

Abstract

OBJECTIVES:

The occurrence of polymyositis (PM) and dermatomyositis (DM) in the general population is largely unknown and unbiased data on clinical and laboratory features in PM/DM are missing. Here, we aim to identify and characterise every PM/DM patient living in southeast Norway (denominator population 2.64 million), 2003-2012.

METHOD:

Due to the structure of the Norwegian health system, all patients with PM/DM are followed at public hospitals. Hence, all public hospital databases in southeast Norway were screened for patients having ICD-10 codes compatible with myositis. Manual chart review was then performed to identify all cases meeting the Peter & Bohan and/or Targoff classification criteria for PM/DM.

RESULTS:

The ICD-10 search identified 3160 potential myositis patients, but only 208/3160 patients met the Peter & Bohan criteria and 230 the Targoff criteria (100 PM, 130 DM). With 56 deaths during the observation period, point prevalence of PM/DM was calculated to 8.7/100 000. Estimated annual incidences ranged from 6 to 10 /1 000 000, with peak incidences at 50-59 (DM) and 60-69 years (PM). Myositis specific antibodies (Jo-1, PL-7, PL-12, signal recognition particle (SRP) and Mi-2) were present in 53% (109/204), while 137/163 (87%) had pathological muscle MRI. Frequent clinical features included myalgia (75%), arthritis (41%) dyspnoea (62%) and dysphagia (58%). Positive anti-Jo-1, present in 39% of DM and 22% of PM cases, was associated with dyspnoea, arthritis and mechanic hands.

CONCLUSIONS:

Our data indicate that the population prevalence of PM/DM in Caucasians is quite low, but underscores the complexity and severity of the disorders.

KEYWORDS:

Dermatomyositis; Epidemiology; Polymyositis

PMID:
24695011
DOI:
10.1136/annrheumdis-2013-205127
[Indexed for MEDLINE]

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