The cause of HLH (Hemophagocytic Lymphohistiocytosis) syndrome varies depending on the type of HLH. There are two main types: Primary HLH and Secondary HLH.
Types and Causes of HLH
| Type of HLH | Cause |
|---|---|
| Primary HLH | Inherited problem of the immune system (familial HLH). |
| Secondary HLH | Immune system disturbance, often triggered by infections or other factors. |
Detailed Explanation of HLH Causes
Primary HLH (Familial HLH)
Primary, or familial, HLH is rooted in genetics. It stems from an inherited problem of the immune system, meaning that the individual is born with a genetic defect that affects how their immune system functions. These genetic defects typically involve genes responsible for the proper function of immune cells, particularly cytotoxic T cells and natural killer (NK) cells. These cells are crucial for eliminating infected or cancerous cells. When these cells don't function correctly, the immune system can become overactive, leading to the destructive inflammation characteristic of HLH.
Secondary HLH
Secondary HLH, on the other hand, is not directly caused by an inherited genetic defect. Instead, it arises when the immune system becomes overly activated due to other factors. Common triggers for secondary HLH include:
- Infections: Viral, bacterial, fungal, or parasitic infections can sometimes trigger an excessive immune response leading to HLH.
- Autoimmune Diseases: Certain autoimmune conditions, where the immune system attacks the body's own tissues, can also lead to HLH.
- Cancers: Some cancers, particularly lymphomas and leukemias, are associated with an increased risk of developing HLH.
- Immunodeficiency States: Conditions that weaken the immune system can sometimes predispose individuals to secondary HLH.
Important Note
Both primary and secondary HLH are serious and potentially life-threatening conditions. Early diagnosis and treatment are essential to improve outcomes.
