Felty's syndrome is a 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.
Goal of therapy is to raise the neutrophil count and prevent recurrent infections, while controlling systemic rheumatoid disease activity.
The neutropenia in FS is defined as a neutrophil count <2 x 10⁹/L (<2000/microlitre) for >6 months.
History and exam
Key diagnostic factors
- presence of risk factors
- joint deformities
Other diagnostic factors
- rheumatoid nodules
- history of vasculitis
- frequent skin and respiratory tract infections
- rheumatoid arthritis (RA) >10 years
- family history of RA
- age >50 years
- white ethnicity
1st investigations to order
- peripheral blood smear
- serum erythrocyte sedimentation rate
- serum CRP
- serum rheumatoid factor
Investigations to consider
- serum antinuclear antibodies
- serum anti-cyclic citrullinated peptide (anti-CCP) antibodies
- ultrasound of abdomen
- CT scan of abdomen
- chest x-ray
- bone marrow biopsy
- virological tests
- Large granular lymphocyte (LGL) syndrome
- Lymphoproliferative disorders
- Myeloproliferative disorders
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