Screening for antibodies against the NXP2 antigen is carried out to investigate polymyositis, dermatomyositis, and overlap syndrome.
Antibodies against the NXP2 protein, also known as MJ antibodies, can be detected in approximately 20% of children and young adults with myositis, often with severe muscle pain (atrophy). It also presents with calcifications, ulcers, and vasculitis. Myositis with positive NXP2 antibodies often responds well to treatment and is not associated with interstitial lung disease or malignancy.
NXP2 antigen corresponds to nuclear matrix protein 2.