A condition in which a buildup of white blood cells harms the liver, spleen and other organs.

Hemophagocytic lymphohistiocytosis is a rare life-threatening condition. The immune system overacts, causing white blood cells to build up. The buildup harms the liver and spleen. The condition affects children and adults. It can be passed down through families, come from an infection or be linked with cancer.

People with this condition might have symptoms only once. Or symptoms can keep coming back. Symptoms include fever, rash, seizures and a liver that's larger than usual.

Treatments include medicines, chemotherapy, getting blood from a donor and stem cell transplant.