This clinical trial is focused on studying the disease known as Dermatomyositis, which is a condition that causes muscle weakness and skin rashes. The treatment being tested in this study is called IgPro20, also known as Hizentra, which is a type of medication made from human blood proteins called immunoglobulins. These proteins help the body fight infections and may also help reduce inflammation in conditions like dermatomyositis.

The purpose of the study is to evaluate how effective and safe IgPro20 is for adults with dermatomyositis. Participants in the study will receive either the IgPro20 treatment or a placebo. The study will last for several weeks, during which participants will have regular check-ups to monitor their health and the effects of the treatment. The study aims to see if the treatment can improve symptoms and overall health in people with dermatomyositis.

Throughout the study, participants will be assessed on their improvement using a scoring system that measures various aspects of their condition, such as muscle strength and skin symptoms. The study will also look at whether participants can reduce their use of other medications, like corticosteroids, which are often used to manage symptoms of dermatomyositis. The results will help determine if IgPro20 is a beneficial treatment option for this condition.