Myositis is a rare disease that involves inflammation of the muscles. This can present with a variety of symptoms such as skin involvement (i.e., rashes), muscle weakness, and other organ involvement. You can also have systemic symptoms such as weight loss, fatigue, and low fever. Causes
Injury, medicines, infection, or an autoimmune disorder can lead to myositis. It can also be idiopathic. Injury - A mild form of myositis can occur with hard exercise. A more severe form of muscle injury, called rhabdomyolysis, is also associated with myositis. This is a condition where injury to your muscles causes them to quickly break down. Medicines - A variety of different medicines can cause myositis. One of the most common drug types that can cause myositis is statins. Statins are drugs that are used to help lower high cholesterol. One of the most common side effects of statin therapy is muscle pain. Rarely, statin therapy can lead to myositis. Infection - The most common infectious cause of myositis is viral infections, such as the common cold. Viruses, such as COVID-19, are also shown to be a rare cause of myositis. Autoimmune - Normally, if you get an infection, your immune system attacks the bacteria/virus that is making you sick. In autoimmune diseases, your immune system gets confused and instead starts attacking your body. In the case of myositis, your immune system attacks your muscles. The three main types of autoimmune myositis are dermatomyositis, polymyositis, and inclusion body myositis.
Swan neck deformity is a deformed position of the finger, in which the joint closest to the fingertip is permanently bent toward the palm while the nearest joint to the palm is bent away from it (DIP flexion with PIP hyperextension). It is commonly caused by injury, hypermobility or inflammatory conditions like rheumatoid arthritis or sometimes familial (congenital, like Ehlers–Danlos syndrome). Pathophysiology
Swan neck deformity has many of possible causes arising from the DIP, PIP, or even the MCP joints. In all cases, there is a stretching of the volar plate at the PIP joint to allow hyperextension, plus some damage to the attachment of the extensor tendon to the base of the distal phalanx that produces a hyperflexed mallet finger. Duck bill deformity is a similar condition affecting the thumb (which cannot have true swan neck deformity because it does not have enough joints). Diagnosis
Diagnosis of swan neck deformity is mainly clinical. MRI of the hand may suggest volar plate attenuation of PIP and extensor tendon damage for DIP  Genetic screening tests such as for CMT disease may also be indicated. Treatment
Splinting for fingers. Passive stretching and clearing the deformity. References
External links
Swan neck deformity at Wheeless Textbook of Orthopedics, a technical review of the condition
Rheumatoid arthritis: Image showing deformities