SNP Shot: Genomic Insights

Familial hemophagocytic lymphohistiocytosis (FHL) is a condition where the immune system becomes overactive. This overactivity leads to the excessive production of activated immune cells, including T cells, natural killer cells, B cells, and macrophages (histiocytes), as well as an overabundance of immune proteins called cytokines. This immune system hyperactivation causes fever and damages organs like the liver and spleen, leading to their enlargement.

In FHL, the bone marrow's blood-producing cells are also destroyed through a process known as hemophagocytosis. This destruction results in anemia (low red blood cell count) and thrombocytopenia (reduced platelet count), which can lead to easy bruising and bleeding problems.

FHL can also affect the brain, potentially causing irritability, delayed skull bone closure in infants, neck stiffness, abnormal muscle tone, coordination problems, paralysis, blindness, seizures, and even coma. Beyond the brain, FHL can lead to issues with the heart, kidneys, and other organs. Furthermore, individuals with FHL face a higher risk of developing blood cancers like leukemia and lymphoma.

The symptoms of FHL typically appear in infancy, although they can sometimes emerge later in life. These symptoms often arise when the immune system overreacts to an infection, but they can also occur without any apparent infection. Without medical intervention, most individuals with FHL only survive for a few months.

Inheritance:

FHL follows an autosomal recessive inheritance pattern. This means that a person must inherit two copies of a mutated gene (one from each parent) to develop the condition. The parents, who each carry only one copy of the mutated gene, are usually unaffected carriers and don't exhibit any signs or symptoms of FHL.