Histiocytosis

What is histiocytosis?

Histiocytosis is a rare group of conditions that occur when your body makes abnormal (mutant) white blood cells called histiocytes. Normal histiocytes help tune up your body’s defenses against multiple pathogens (like viruses, bacteria, fungi and parasites). But too many histiocytes can cause problems in your immune system, including inflammation in your body’s tissues. The inflammation can lead to organ damage.

The excess, abnormal histiocytes may build up in your lymph nodes, skin, bones, lungs, liver, spleen or other body parts. They may affect one part of your body (single system). Or they may affect many parts of your body (multisystem). While histiocytosis isn’t a cancer, it may behave and cause symptoms like cancer.

The variety in symptoms and severity can make histiocytosis challenging to diagnose in a timely fashion.

Types of histiocytosis

There are more than 100 subtypes of histiocytosis, but the three most common are:

• Langerhans cell histiocytosis (LCH): LCH is the most common type of histiocytosis. It’s most common in children, affecting 5 to 9 children out of every 1 million. Usually, it’s mild and asymptomatic (doesn’t cause severe symptoms), but it can be debilitating and life-threatening in some cases.
• Erdheim-Chester disease (ECD): ECD primarily affects adults. It’s rather rare. Similar to LCH, ECD ranges in severity from mild to potentially life-threatening.
• Rosai-Dorfman disease (RDD): Like LCH, RDD mostly affects children but can also affect adults. Only about 1 in 200,000 people receive this diagnosis. The most common type (classical RDD) causes your lymph nodes to swell. The other type is called extranodal RDD. Extranodal RDD affects organs other than your lymph nodes. The excess histiocytes may build up in your skin, bones or other places.

How rare is histiocytosis?

Histiocytosis is a rare group of disorders. The malignant forms account for less than 1% of all cancer diagnoses affecting soft tissue and lymph nodes.

What are the symptoms of histiocytosis?

Symptoms vary depending on which organs and tissues contain excess histiocytes. The extent of the tissue damage also plays a role.

Signs and symptoms of histiocytosis include (but aren’t limited to):

• Skin rashes, including on hairy part of the head (cradle cap) or diaper area in little babies
• Fever.
• Fatigue.
• Headache.
• Cough or shortness of breath.
• Unexplained weight loss.
• Bone pain.
• Swollen lymph nodes.
• Vision changes or bulging eyes.
• Frequent peeing (urination) and excessive thirst.
• Growths on your skin (including on your eyelids).
• Trouble concentrating or remembering.
• Problems with coordination and balance.

Sites involved

Symptoms correspond with the places in your body where histiocytes build up. The most common sites vary depending on the type of histiocytosis.

Langerhans cell histiocytosis

• Bones.
• Skin.
• Lymph nodes.
• Liver.
• Spleen.
• Mouth.
• Lungs.
• Central nervous system.

Erdheim-Chester disease

• Long bones (especially in your legs).
• Eyes.
• Central nervous system.
• Lungs.
• Heart.
• Blood vessels.
• Kidneys.
• Organs in the area behind your abdomen (retroperitoneum).

Rosai-Dorfman disease

• Lymph nodes (especially in your neck, but in other places, too).
• Skin.
• Soft tissue.
• Upper respiratory tract.
• Bones.
• Retroperitoneum.
• Eyes.

What causes histiocytosis?

Scientists don’t know what causes histiocytosis. Still, they’ve identified genetic mutations that likely play a role. Cells contain genetic material, or instructions, that tell them how to behave. Mutations, or changes, in a cell’s instructions can cause it to behave abnormally. For example, a genetic mutation may cause a cell — like a histiocyte — to copy itself and spread.

Identifying gene mutations has allowed researchers to develop new treatments for histiocytosis. These treatments prevent harmful cell changes that allow histiocytes to grow out of control.

How is histiocytosis diagnosed?

Your healthcare provider will perform a physical exam and ask you about your medical history. The tests you’ll need depend on your symptoms and which organs are likely harmed by the excess histiocytes.

Tests include:

• Imaging procedures: Your provider may perform a special type of scan called an FDG PET/CT scan. This procedure can detect tumors throughout your body. Other imaging procedures you may need include a CT scan, MRI, bone scan, ultrasound, X-ray or echocardiogram.
• Lab tests: Your provider may test fluid samples, like your blood or urine, for signs of histiocytosis. They’ll check your blood cell counts and look for specific hormones or proteins that provide clues about your organ function. Problems with how an organ is working may indicate excess histiocytes in that organ.
• Biopsy: Your provider may perform a biopsy. They’ll remove and analyze a tissue sample beneath a microscope to see if you have histiocytosis. They’ll look for specific genetic mutations associated with histiocytosis. If they can’t access tissue through a biopsy, they may test the genetic material in your blood. This is called liquid biopsy.

How is histiocytosis treated?

Treatment depends on many factors, including:

• How severe your symptoms are.
• Whether you have one or many lesions (abnormal tissues).
• Where the lesions are located in your body.
• If the tumors are cancerous or benign.

Treatments include:

• Watch and wait: Your healthcare provider may monitor your condition if your histiocytosis is mild and you’re not experiencing symptoms.
• Surgery: Surgery may be an option if the histiocytes are only in one part of your body.
• Radiation therapy: Radiation therapy uses a machine that directs energy beams toward lesions. The radiation beams destroy the cells and slow tumor growth. Sometimes, radiation therapy helps with symptom relief.
• Chemotherapy: Chemotherapy sends chemicals throughout your bloodstream to destroy excess histiocytes. Your healthcare provider may recommend chemotherapy if the excess histiocytes are spread throughout your body.
• Corticosteroids: Corticosteroids, like prednisone, can reduce the inflammation associated with histiocytosis. You may receive corticosteroids alone or in combination with other treatments, like chemotherapy.
• Immunotherapy: Immunotherapy bolsters your immune system so it’s better able to identify and destroy harmful cells, like abnormal histiocytes.
• Targeted therapy: Targeted therapy treats histiocytosis associated with certain genetic mutations.

Is histiocytosis curable?

It depends. Many people with histiocytosis achieve “durable remission,” which means they don’t have any signs or symptoms from their illness. Surgery can cure some forms of histiocytosis when the histiocytes are only in one part of your body. Your healthcare provider will recommend a schedule for follow-up visits to catch any disease that returns (recurs).

If your form of histiocytosis isn’t curable, your healthcare provider can recommend a treatment plan to manage the condition.

Can histiocytosis be prevented?

Histiocytosis isn’t preventable, but treatment can help manage your symptoms.

How can I reduce my risk?

Stopping smoking can reduce your risk of LCH involving your lungs. Quitting smoking or choosing not to smoke can also help you respond better to treatment. Your healthcare provider can provide you with smoking cessation referral programs.

What is the prognosis for histiocytosis?

The likely outcome of your condition depends on multiple factors. For some people, histiocytosis resolves on its own. For example, in 40% of people with RDD, the condition gets better without treatment. LCH often resolves on its own in children when the condition only affects one part of the body (localized LCH).

In other instances, histiocytosis in both children and adults requires intensive treatment and careful monitoring. In more severe cases, histiocytosis can lead to organ damage that’s potentially fatal.

Ask your healthcare provider about your prognosis based on your unique diagnosis.

What questions should I ask my doctor?

• What form of histiocytosis do I have?
• Will I need treatment?
• What treatment options would you recommend?
• What treatment side effects should I expect?
• What’s the likely outcome of treatment?
• Is my condition curable?

A note from Cleveland Clinic

Histiocytosis refers to many rare blood disorders where white blood cells (histiocytes) build up in tissue. This includes conditions that range from mild and asymptomatic to potentially fatal. Everyone with histiocytosis has excess histiocytes in tissue that cause inflammation. Still, symptoms, treatments and outlook vary greatly even among people with the same type of histiocytosis. Your healthcare provider is your best resource for understanding what’s unique about your diagnosis. It’s essential to ask questions so you understand your diagnosis and care plan.