The cause of<unk>  is unknown, but it has been found to be more common in those with chronic rheumatoid arthritis. Some patients share the HLA-DR4 serotype. This<unk>  is mostly present in people having extra articular manifestations of rheumatoid arthritis. People with this<unk>  are at risk of infection because they have a low white blood cell count.
Felty's syndrome
SUNCT syndrome
Crome syndrome
Eosinophilia–myalgia syndrome
Michels Caskey syndrome
Roemheld syndrome
Mendelson's syndrome
MASA syndrome