The aim of this study is to investigate the hand function in patients with poly-and dermatomyositis and compare this to healthy individuals and norm values and secondly if hand function correlates to activity performance and health related quality of life.

The study is a cross-sectional study. To assess hand function the investigators will measure grip force with Grippit and arm/hand mobility using EPM-ROM scale. The activity performance will be measured with Myositis Activities Profile and health related quality of life will be assessed with SF-36.

The investigators' hypothesis is that hand function is reduced in comparison to the healthy population and that hand function affects both activity performance and health related quality of life.

Inclusion Criteria:

• Patients with definite or probable polymyositis or dermatomyositis (according to criteria by Bohan and Peter) were included in the study

Exclusion Criteria:

• Other diseases or injuries that could affect arm/hand mobility and grip force for example other rheumatological or neurological disease.

A total of 50 patients diagnosed with polymyositis or dermatomyositis were identified through the myositis registry at the rheumatology clinic at Karolinska University Hospital, Stockholm, Sweden.