Introduction
Secondary hemophagocytic lymphohistiocytosis, or acquired hemophagocytic lymphocytosis, is an uncommon and sometimes fatal condition affecting infants, teenagers, and adults. It is also known as HLH or hemophagocytic syndrome. HLH is not a single illness; it is a group of immune system disorders that can induce infections, cancer, or rheumatic diseases.
The immune system abnormalities in HLH can cause organ failure and possibly death. This system is a complex network of cells and tissues made up of numerous parts. White blood cells are essential for communicating with each other and other cells in the body by producing cytokines, which are chemical "messengers." When white blood cells perform abnormally in HLH, they usually overproduce cytokines and may harm organs, including the liver, spleen, bone marrow, and brain. HLH can cause severe organ damage and even death if it is not promptly diagnosed and treated. HLH occurs in two primary forms, such as primary and secondary HLH. This article briefly addresses secondary hemophagocytic lymphohistiocytosis.
How to Differentiate Between Primary and Secondary HLH?
An inherited problem of the immune system causes primary or familial HLH. It often runs in families and typically occurs during infancy or early childhood. Secondary or acquired HLH develops when the immune system does not function normally. Both types of HLH are life-threatening.
What Is Secondary HLH?
Secondary or acquired HLH is a heterogeneous disorder associated with several types of infections and metabolic, neoplastic, and rheumatologic conditions. It is usually diagnosed in adults and older children. Although secondary HLH is not inherited, it can develop when the immune system is disturbed (e.g., by infections). Histiocytes and lymphocytes are white blood cells that attack other blood cells. Abnormal blood cells then accumulate in the spleen and liver. It causes swelling in the liver and the spleen. Acquired HLH is a fatal condition. If left untreated, it may result in death within weeks or months. The incidence of secondary HLH (the rate at which it develops in the population) is unknown.
What Causes Secondary HLH?
HLH is a rare condition, and studies to figure out the causes are underway. There are two forms of HLH: familial and acquired. Familial HLH is passed down from the parents to the offspring. Adults who have acquired HLH may have:
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Viral infections, especially Epstein-Barr virus.
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Bacteria or fungal infections.
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Several cancers, including T-cell lymphoma.
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Autoimmune conditions.
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Immune system-suppressing medications.
If a virus is the root cause of acquired HLH, people may also have X-linked lymphoproliferative disorder (XLP).
What Are the Symptoms of Secondary HLH?
The symptoms of acquired HLH can resemble those of various medical diseases. Consult a physician for a diagnosis of HLH. Fever and an enlarged spleen are the two most typical signs of acquired HLH. There are other possible symptoms, including:
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Enlarged liver.
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Jaundice (Yellow color of eyes and skin).
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Swollen lymph nodes.
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Lung problems such as coughing and difficulty breathing.
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Digestive problems like diarrhea, vomiting, and stomach pain.
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Nervous system problems like headaches, weakness, vision disturbances, and trouble walking.
Additional symptoms, such as irritability and failure to flourish, may appear in young children and neonates. It indicates that they don't develop and grow normally.
How Is Secondary HLH Diagnosed?
History and Physical Examinations: The healthcare professional will diagnose HLH based on individual's symptoms, physical exam findings, and the results of several lab tests. Persistent fever is a common symptom. The most important physical signs are an enlarged liver or spleen (placed in the abdomen). The doctor may perform blood tests to check for the following:
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Low levels of natural killer cells, which are white blood cells.
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Low levels of platelets, other white blood cells, red blood cells, and clotting cells.
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Low levels of the clotting protein called fibrinogen.
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High levels of triglycerides (fat) in the blood.
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High levels of ferritin, a protein that stores iron.
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Increased levels of a molecule called CD25, which rises in the blood when the immune system is functioning.
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Signs of infection.
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Genetic variations.
Diagnostic Investigations: The following tests are used by physicians to identify HLH and provide a personalized treatment strategy.
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Blood Tests - These include blood cell counts, liver function tests, infection tests, and markers of immune system activation, including ferritin and soluble IL-2 receptor levels.
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Bone Marrow Biopsy - Bone marrow is the soft tissue found in the middle of some large bones. Bone marrow produces blood cells. A needle is used to extract a sample of the bone marrow for this test. The tissue is examined under a microscope.
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Lumbar Puncture - Doctors do this procedure to collect cerebrospinal fluid to determine whether HLH is harming the brain.
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Imaging Studies - These include X-rays, CT (computed tomography) scans, ultrasounds, and magnetic resonance imaging (MRI).
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Other Tests - These include blood cultures and genetic testing, which are blood samples to examine for infection in the blood.
How Is Secondary HLH Treated?
Secondary HLH treatment is determined more by the severity of the condition and its symptoms than by its categorization. Prompt treatment is essential for HLH patients because the condition is generally fatal. The first treatments are often used to reduce body inflammation. These treatments suppress the immune system, which helps reduce the body's damage. Treatment options for persistent acquired HLH include:
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Chemotherapy drugs (cancer drugs).
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Immunotherapy drugs (medicine that affects the immune system).
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Steroids (drugs that fight inflammation).
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Antibiotic drugs.
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Antiviral drugs.
Is There a Cure for HLH?
The doctor may recommend a hematopoietic stem cell transplant if medical therapies fail. In this process, healthy bone marrow cells from a donor are used to replace damaged bone marrow cells. In most cases, a stem cell transplant can treat HLH. Secondary HLH is usually curable by treating the underlying condition and adding immunosuppressive or immunomodulatory medication.
Conclusion
Secondary or acquired hemophagocytic lymphohistiocytosis is a potentially fatal disease that can kill a person in a matter of weeks or months if it is not treated. So, it's important to let the doctor know if the symptoms keep coming back, get worse, or if any new ones show up. Although there is no way to prevent HLH, medical professionals' understanding of the disease has led to advancements in therapy. The majority of kids who receive effective treatment go on to lead regular lives.
