Rare, extra-articular manifestation of rheumatoid arthritis (RA), characterised by persistent, idiopathic neutropenia and, in some cases, splenomegaly. Estimated to occur in <1% of RA patients.
Tends to occur in the fifth to seventh decades of life, typically in white patients who have had long-standing seropositive, erosive RA.
A clinical diagnosis with no specific diagnostic test; other causes of neutropenia should be excluded.
Cause of neutropenia is multi-factorial and is thought to result from an imbalance between neutrophil production in the bone marrow and increased destruction in the peripheral blood, or both.
Goal of therapy is to raise the neutrophil count and prevent recurrent infections, while controlling systemic rheumatoid disease activity.
First described by A.R. Felty in 1924, Felty's syndrome (FS) is a rare, extra-articular manifestation of rheumatoid arthritis. It is characterised by persistent, idiopathic neutropenia and frequently (>90% cases) by splenomegaly.   The neutropenia in FS is defined as a neutrophil count <2 x 10^9/L (<2000/microlitre) for >6 months. 
Kingston upon Thames
DH declares that she has no competing interests.
Queen Elizabeth Hospital
GC is the author of one reference cited in this monograph.
Consultant Rheumatologist and Honorary Senior Clinical Lecturer in Rheumatology
Selly Oak Hospital
SB declares that he has no competing interests.
Mary Pack Arthritis Program
Clinical Associate Professor
University of British Columbia
AK is the author of a study referenced in this monograph.
Professor and Vice Chair
Department of Medicine
University of Wisconsin Hospital
AB declares that he has no competing interests.
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