Introduction

Felty syndrome (FA) is associated with Rheumatoid arthritis (RA). It was first described by Augustus Felty. This disease can be asymptomatic in some individuals and life-threatening in others. Rheumatoid arthritis occurs when the body's immune system begins to fight the membranes surrounding joints in the body, especially small joints like the shoulder joint, knee joint, etc. According to WHO, 18 million people are affected by RA, 70% are women and 55% are above 55 years old.¹

The cause of RA is unknown, However, Felty syndrome is characterized by low number of Neutrophils (Neutropenia), and an enlarged spleen.

This article will discuss the infection associated with the disease. 

Pathophysiology

The pathophysiology involves many processes, including genetic or neutropenia processes. Neutrophils are one of the components of the immune system, produced in the immune system and transported through the blood to tissues. In the genetic pathway, there is an antigen called human leukocyte antigen (HLA-DR4) which can worsen autoimmune activity. A complex autoimmune activity leads to decreased production of neutrophil increasing the removal of neutrophil from the circulatory system (neutropenia) hence causing infections.

What is an Infection?

Infections occur when microbes - such as fungi, bacteria, viruses and protozoa - enter the human body, multiply in areas where they are not normally present and grow uncontrollably. This overgrowth can lead to cell damage and disrupt normal bodily functions. When this occurs, immune cells known as white blood cells (WBC) will fight the infection to eliminate the microorganisms that inhibit the body’s defence mechanisms. However, for those with Rheumatoid arthritis, the immune system is already weakened due to the medications taken.² 

The Role of Neutrophils in Controlling Infections

Neutrophils play an important role in the homeostasis of the immune system. When an infection occurs, the neutrophils migrate to the infection site through a process called chemotaxis with the aid of chemokines. When they get to the site, the neutrophils will engulf the microbe responsible for the infection through a process called phagocytosis. Neutrophils contain some substance which aids the destruction of the pathogen, these substances include: lysozyme, defensins, myeloperoxidase.

The neutrophils release extracellular fibers known as neutrophils extracellular traps (NETs), containing histones, DNA and antimicrobial proteins. These components aid in the killing of the pathogens extracellularly and prevent the spread to other tissues or cells. 

Neutrophil apoptosis is another process in which infections are resolved. This process prevents the release of neutrophil cytotoxic substances that can cause tissue damage by engaging macrophages and dendritic cells.

Bacterial Infections Affecting Felty Syndrome

Bacteria are prokaryotic organisms found everywhere in the environment, and some make up the body’s gut. some of them are normal flora found in the body. Bacterial infection occurs due to the infectivity, pathogenicity and ability to cause disease(virulence).³

Bacteria are grouped into Gram-positive and Gram-negative categories. Infections can occur in various parts of the body, including the skin, mouth (respiratory tract), and urinary tract. 

• Skin infections can lead to soft tissue infections 
• Respiratory tract infections can cause pneumonia and bronchitis 
• Urinary tract infections (UTIs) occur when bacteria infect the bladder or urethra

If these infections are left untreated, it could lead to a life-threatening disease known as sepsis. Examples of the microbes involved in bacterial infection are: Staphylococcus aureus, Haemophilus influenzae, Pseudomonas aeruginosa and Streptococcus app.⁴

Viral Infections Affecting Felty Syndrome

This is another form of infection that affects individuals with Felty syndrome. They include;

• Cytomegalovirus⁵ (CMV)
• Epstein-Barr Virus (EBV)
• Varicella-Zoster Virus (VZV)
• Herpes Simplex Virus (HSV)
• Influenza

Opportunistic fungal infections, such as candidiasis and aspergillosis, can also affect individuals with Felty Syndrome.

Symptoms of Infection

• Inflammation
• Fever
• Pains
• Skin discoloration 

Diagnosis

• Complete Blood Count (CBC): an important aspect in determining the absolute neutrophil count (ANC) which is a key factor in diagnosing Felty syndrome. Neutropenia could be a result of bacterial infection.  Continous monitoring of the ANC can aid in early diagnosis of Felty Syndrome, as it may be affected by various factors, such as medications
• Imaging studies: aid in the visualisation of organs like the spleen, which may be enlarged, and also detect abnormalities in the joints. In some cases, joints can be exposed to ultraviolet rays to identify any damage or irregularities, aiding in diagnosis
• Microbiological testing: used to identify a positive rheumatoid factor (RF). In patients with Felty syndrome, anti-histone antibodies are present in about 83% of cases. This can be used to detect antinuclear antibodies, anti-histone antibodies and other markers related to autoimmune disorders⁶ 

Treatment

The treatment for Felty Syndrome focuses on managing rheumatoid arthritis and neutropenia to prevent infections. These treatments include:

• Disease-modifying antirheumatic drugs (DMARDs): These are administered to patients with rheumatoid arthritis associated with neutropenia to help control inflammation and slow disease progression
• Anti-fungal and broad spectrum antibiotics: These are used to prevent or treat infections, given the increased susceptibility to infections due to neutropenia⁷ 

Summary 

In patients with Felty syndrome, infections can occur due to neutropenia, which makes them more susceptible to viral, bacterial and fungal infections. It is crucial to regularly monitor the Absolute Neutrophil Count (ANC) to assess the risk of infections and manage neutropenia effectively. 

FAQs

What is the triad of Felty's syndrome?

The triad of Felty’s syndrome are Rheumatoid arthritis, neutropenia and splenomegaly. 

How is Felty syndrome treated?

Felty syndrome is treated using DMARDs and antibiotics.

What are the symptoms of felty syndrome?

• Pains
• Inflammation
• Recurrent infections
• Fatigue
• Weight loss
• Fever
• Anaemia etc.