Hemophagocytic lymphohistiocytosis, also called HLH, is an immune deficiency disorder. In this type of disorder, part of the immune system is missing or defective. That means the body can’t fight infections as it should. As a result, a person with HLH may have frequent infections that are generally more severe and last longer than usual.
With HLH, certain white blood cells, (T lymphocytes and macrophages), are not able to be switched off and build up in organs including the skin, spleen, and liver. These cells then destroy other blood cells such as red blood cells, platelets and neutrophils, along with causing damage to affected organs.
There are two types of HLH. “Primary,” or “familial,” HLH is caused by an inherited problem of the immune system. “Secondary” HLH can occur when the immune system is disturbed (e.g., infections), but not necessarily because of an inherited condition. Both types of HLH are life-threatening. HLH can lead to liver failure, breathing problems, inflammation in the brain, and the inability to fight infection.
HLH happens more often in infants and children. But it can occur at any age, including in the teenage years and adulthood.
HLH is considered a rare disease. Statistics say it occurs in about one in 50,000 children. Because of that, many healthcare providers are unfamiliar with its symptoms, and it often goes undiagnosed for too long.
HLH can be challenging to diagnose because the initial symptoms may mimic common infections. Symptoms of HLH that you may notice in your child include:
- Persistent fevers
- Enlarged lymph nodes
- Jaundice (yellow color of your skin and eyes
- Coughing, trouble breathing
- Altered mental status
Other issues that your child’s doctor may find include:
- Liver failure
- Low blood counts
- Enlarged liver
- Enlarged spleen
HLH can only be diagnosed with proper blood tests in the appropriate clinical setting.. Doctors might collect some fluid from the spinal canal to look for HLH in the brain. It is important to remember certain malignancies (including leukemia and lymphoma) can mimic HLH, therefore these conditions should be appropriately investigated during the work-up of a suspected patient with HLH.
Other tests that might be performed include:
- Bone marrow testing
- CT scans
- PET scan (to look for malignancy)
- Tests to look for infections that can be associated with HLH
- Special blood tests that can be done to quickly screen patients for the genetic causes of HLH
- Genetic testing
Prompt treatment is very important for patients with HLH, as the condition is often fatal. The first treatments are typically used to stop the inflammation in the body. These treatments suppress the immune system which helps decrease the damage to a patient’s body.
Treatment may include:
- Steroids plus chemotherapy
- Antibody therapy to destroy certain immune cells
- Medicines that suppress the immune system
- Medicines to help treat any infections that are present and to prevent new infections
With treatment, HLH may come under control after a few weeks. However, it may flare again later, especially as treatment is decreased and a patient may need further treatment.
Often, patients with primary HLH may need a bone marrow transplant (BMT). Often patients who have a successful BMT go on to lead full, productive lives.