What is Felty's syndrome?

Felty's Syndrome: Clinical Features, Diagnosis, and Management

Felty's syndrome is characterized by the triad of rheumatoid arthritis, neutropenia, and splenomegaly, representing a rare but severe extra-articular manifestation of rheumatoid arthritis that occurs in less than 1% of rheumatoid arthritis patients. 1, 2

Clinical Features

• Felty's syndrome typically presents with the classic triad of:

  • Rheumatoid arthritis (often longstanding and seropositive)
  • Neutropenia (can range from mild to severe)
  • Splenomegaly (can range from mild to massive) 1

• Patients often exhibit severe joint destruction despite moderate or absent active joint inflammation 2

• Common extra-articular manifestations include:

  • Recurrent bacterial infections (due to neutropenia)
  • Rheumatoid nodules
  • Lymphadenopathy
  • Hepatic involvement
  • Vasculitis
  • Leg ulcers
  • Skin pigmentation 2

• Atypical presentations can occur where neutropenia and splenomegaly precede clinical evidence of arthritis, known as "non-articular Felty's syndrome" 3, 4

Diagnostic Approach

• Laboratory investigations should include:

  • Complete blood count with differential to confirm neutropenia
  • Inflammatory markers (ESR, CRP)
  • Autoimmune panel including rheumatoid factor (RF) and anti-cyclic citrullinated peptide (anti-CCP) antibodies 5

• Imaging studies:

  • Abdominal ultrasound or CT scan to confirm splenomegaly
  • Joint radiographs to assess for erosive changes consistent with rheumatoid arthritis 5

• Serological findings typically include:

  • Positive rheumatoid factor (>95% of patients)
  • Positive antinuclear antibodies (47-100% of patients)
  • Positive anti-CCP antibodies
  • HLA-DR4*0401 antigen in approximately 78% of patients 2

• Differential diagnosis should exclude:

  • Myelodysplastic syndromes
  • Systemic lupus erythematosus
  • Leukemia
  • Infectious causes of splenomegaly 1, 5

Management

• Treatment should target both the underlying rheumatoid arthritis and neutropenia 1

• First-line therapy:

  • Disease-modifying anti-rheumatic drugs (DMARDs), with methotrexate having the most extensive clinical experience 2
  • Corticosteroids (prednisone 10-20 mg/day) may be used for acute management 5

• For refractory cases:

  • Granulocyte colony-stimulating factor (G-CSF) has shown encouraging results for managing neutropenia 2
  • Biologic treatments should be considered for patients not responding to conventional therapy 1

• Splenectomy:

  • Results in immediate improvement of neutropenia in approximately 80% of patients
  • However, the rate of infection decreases to a lesser degree
  • Should be reserved for cases refractory to medical management 2

Monitoring and Follow-up

• Regular monitoring of complete blood counts to assess neutrophil levels 5
• Assessment of rheumatoid arthritis disease activity 5
• Vigilance for signs of infection, especially in patients with severe neutropenia 2

Special Considerations

• Some patients (approximately 30%) with Felty's syndrome have large granular lymphocyte (LGL) expansion 2
• Patients may present with neutropenia and splenomegaly before developing clinical arthritis, so serological testing for rheumatoid arthritis should be performed in patients with unexplained neutropenia and splenomegaly 4, 6
• Spontaneous remission of the syndrome can occur 2