Felty Syndrome

Overview

Felty syndrome is a rare condition that can happen in people who already have rheumatoid arthritis, a long-term condition where the immune system attacks the joints. Felty syndrome is recognised by three features appearing together: rheumatoid arthritis, an enlarged spleen, and a low number of white blood cells called neutrophils. Neutrophils are the cells your body uses to fight infection, so when they are low you may catch infections more easily. Felty syndrome is not a separate kind of arthritis. It is a complication of rheumatoid arthritis, and it usually develops in people who have had arthritis for many years.

No, it is rare. It is thought to affect fewer than 1 in 100 people with rheumatoid arthritis, and doctors see it much less often than they used to. Many general practice doctors may never see a case in their whole career.

It mostly affects adults who have had rheumatoid arthritis for a long time, often 10 years or more. It is more likely in people whose arthritis has been severe, who have joint damage or other body-wide effects of arthritis, and who have certain blood antibodies (proteins the immune system makes) such as rheumatoid factor. It is usually diagnosed between the ages of about 50 and 70. It is very rarely seen in children.

Symptoms

Common symptoms

• Feeling generally unwell, tired, or lacking energy
• Infections that keep coming back or take longer to clear, such as chest, skin, urine, or throat infections
• A feeling of fullness or mild pain under the left ribs, from an enlarged spleen
• Weight loss you did not intend
• A low-grade temperature or fevers, sometimes with shivering
• Mouth ulcers or sore gums
• Dry or red eyes
• Painful open sores on the lower legs (leg ulcers)
• Small patches of darker skin on the legs
• The usual joint pain and stiffness of rheumatoid arthritis

Symptoms in children

• Felty syndrome is essentially not seen in children; it is a condition of adults with long-standing rheumatoid arthritis.
• Children with juvenile arthritis can develop low blood counts or spleen problems for other reasons, so any such finding in a child should be checked by a specialist.

Symptoms in older adults

• Infections can become serious faster, so even a mild fever deserves a same-day call to a doctor.
• Tiredness, weight loss, and feeling low may be mistaken for normal ageing, so mention any change to your doctor.
• Older adults may not always develop a high temperature when they have an infection, so watch for confusion, shivering, or feeling suddenly much worse.

Causes

Main causes

• Felty syndrome is an autoimmune complication of rheumatoid arthritis, meaning the immune system mistakenly attacks the body's own tissues.
• The exact cause is not fully understood, but the immune system appears to become overactive in a way that affects the spleen and white blood cells.
• The spleen becomes overactive and removes white blood cells from the blood too quickly, which lowers the neutrophil count.
• The immune system may also make antibodies that attack neutrophils or stop the bone marrow from making them normally.

Risk factors

• Having had rheumatoid arthritis for many years, often 10 or more
• Severe rheumatoid arthritis, especially with joint damage or effects on other parts of the body
• A positive test for rheumatoid factor or anti-CCP antibodies (immune proteins linked to arthritis)
• Certain inherited immune-system markers, which are more common in some families
• Being in mid-to-later adult life
• Smoking, which is linked to more severe rheumatoid arthritis

When to see a doctor

See a doctor urgently if:

• You have a fever, especially with shivering or shaking chills
• You have signs of an infection that is getting worse, such as a chest infection, urine infection, or a red, hot, painful area of skin
• You feel suddenly much more unwell, confused, or very weak
• You have severe pain or new swelling under the left ribs

Book a routine appointment if:

• You keep getting infections or infections that take a long time to clear
• You have unintentional weight loss or persistent tiredness
• You notice new mouth ulcers, dry eyes, or sores on your legs
• You have had rheumatoid arthritis for many years and want to review your overall care
• You are due a routine arthritis review or blood test

Diagnosis

There is no single test for Felty syndrome. A doctor makes the diagnosis by putting together your history of rheumatoid arthritis, a physical examination (including checking for an enlarged spleen), and blood test results showing a low neutrophil count. They will also check for other reasons why your white cell count or spleen might be abnormal, because many other conditions can cause similar findings.

Tests that may be done

• A full blood count, to measure white cells (including neutrophils), red cells, and platelets
• A blood film, where a sample is looked at under a microscope to see the shape and number of blood cells
• Blood tests for rheumatoid factor and anti-CCP antibodies
• Liver and kidney function tests, and markers of inflammation
• Blood or other cultures if you have a fever, to look for infection
• An ultrasound scan or CT scan to check the size of the spleen
• In some cases, a bone marrow sample (a small biopsy taken with a needle) to rule out other causes of a low white cell count

What to expect at your appointment

You will usually be referred to a rheumatologist (a doctor who specialises in arthritis and immune conditions) and possibly a haematologist (a doctor who specialises in blood). You may need repeat blood tests over months so your team can see the pattern. Expect questions about infections you have had, and be ready to report any fever promptly. The process can feel slow, but the aim is to be thorough and rule out other conditions.

Treatment

There is no cure for Felty syndrome, but it can be managed. Treatment has two main goals: keeping your rheumatoid arthritis well controlled, and lowering the risk and impact of infection. Care is usually shared between your general practice team, a rheumatologist, and sometimes a blood specialist.

Self-care at home

• Wash your hands often, and ask people around you to do the same
• Keep your mouth clean and see a dentist regularly; tell your dentist about your condition
• Look after your skin and treat cuts and grazes promptly
• Keep a thermometer at home and check your temperature if you feel unwell
• Avoid close contact with people who have active infections such as flu or chickenpox
• Stop smoking if you smoke, and ask for help to do so
• Keep your arthritis appointments and blood tests even when you feel well
• Note down any fevers, infections, or new symptoms in a simple diary to share with your doctor

Medical treatments

Doctors aim to control the underlying rheumatoid arthritis, because better arthritis control often improves the blood counts. This usually means arthritis medicines that calm the immune system, chosen and monitored by a rheumatologist. Your team may also use treatments that encourage the bone marrow to make more white blood cells, and antibiotics to treat infections quickly when they occur. Some people are given regular antibiotics for a period to prevent repeated infections. Vaccinations are an important part of the plan. Because immune-calming treatment can itself affect infection risk, your team will balance the benefits and monitor you closely with regular blood tests. Always check with your doctor or pharmacist before starting any new medicine, including over-the-counter ones and herbal remedies.

When is surgery considered?

Surgery is only considered in a small number of people. Removing the spleen (an operation called splenectomy) may be discussed if you have very low white cell counts and repeated severe infections that do not improve with other treatment. It is a big decision with its own risks, including a lifelong higher risk of certain infections, so it is only recommended after careful discussion with your specialist team. If your spleen is removed, you will need extra vaccinations and lifelong advice about preventing infection.

Living with this condition

Many people with Felty syndrome live full lives with regular monitoring. The main day-to-day focus is noticing infections early. Keep a thermometer at home, know the warning signs, and contact your doctor the same day if you have a fever. Plan activities around your energy levels, pace yourself, and build in rest. Keep a simple record of your appointments, blood test results, and any infections so you can share them with your care team.

Lifestyle tips

• Build gentle, regular movement into your week, such as walking, swimming, or stretching, and rest when your joints or energy need it
• Protect your sleep, and aim for a steady routine
• Avoid smoking, and limit alcohol
• Keep up with dental check-ups and eye checks
• Ask your doctor or pharmacist about which vaccinations are right for you
• Carry a card or note listing your condition and medicines in case of emergency

Diet and exercise

There is no special diet that cures Felty syndrome, but eating a balanced diet with plenty of vegetables, fruit, whole grains, and protein helps your body cope with infection and fatigue. Some people find certain foods affect their arthritis symptoms; if so, discuss it with your doctor or a dietitian rather than cutting out whole food groups. Gentle exercise helps joints and mood. A physiotherapist can suggest safe exercises for your joints, and your doctor can advise on how much activity is right for you, especially during a flare or an infection.

Mental health and emotional wellbeing

Living with a long-term condition, repeated infections, and fatigue can feel worrying, frustrating, or lonely. Feeling anxious about fevers or infections is understandable. Talk to your doctor if low mood, worry, or poor sleep is affecting your daily life, as there is effective support available. If you ever have thoughts of harming yourself, please contact your local emergency number or a crisis support service in your area straight away, and reach out to someone you trust.

Prevention

You cannot prevent Felty syndrome directly, and nothing you did caused it. The best available approach is to keep rheumatoid arthritis well treated and monitored, which reduces the chance of severe complications. Seeing your arthritis team regularly and reporting new symptoms early helps problems get picked up sooner.

Vaccines

Vaccination is an important part of staying well when your immune system is affected by arthritis or its treatment. Ask your doctor or pharmacist which vaccinations are recommended for you, such as yearly flu, pneumonia, and other routine adult vaccines. Some vaccines are not suitable if you are on immune-calming treatment or have had your spleen removed, so always check with your care team first — and let them know if anyone in your household is due a live vaccine.

Screening programmes

There is no national screening programme for Felty syndrome. Instead, people with long-standing rheumatoid arthritis usually have regular blood counts as part of their arthritis care, which can pick up a low white cell count early. If you have had your spleen removed, you will need lifelong monitoring and specific vaccinations; your team will explain the schedule.

Complications

If left untreated

• Infections that are more frequent and can become serious quickly, including chest, skin, urine, and bloodstream infections
• A higher risk of sepsis, a whole-body reaction to infection that is a medical emergency
• Leg ulcers and slow-healing skin wounds
• Anaemia (a low red blood cell count) causing tiredness and breathlessness
• A low platelet count, which can cause bruising or bleeding more easily
• Ongoing joint damage from uncontrolled rheumatoid arthritis
• A slightly increased risk of some blood cancers, such as lymphoma, which is rare and is monitored by your specialist team

Long-term outlook

The outlook for most people is cautiously positive. Because rheumatoid arthritis is now treated earlier and more effectively, Felty syndrome has become much less common, and many people who develop it do well with monitoring and treatment. Some people need extra treatment or, rarely, spleen surgery, and a small number have repeated infections. Working closely with your care team, reporting fevers promptly, and keeping up with appointments makes a real difference.

Find support

External links open third-party websites. Ruqelo Health is not responsible for external content. Listing an organisation does not imply endorsement.