Hemophagocytic Syndrome, Hemophagic Histiocytosis

Hemophagocytic syndrome is a form of histiocytosis which is a general name for a group of syndromes. These syndromes all include an abnormal increase in the number of certain immune cells, called histiocyte cells. Histiocyte cells include monocytes, macrophages, and dendritic cells. The extra immune cells may form tumors, which can affect various parts of the body.

The term hemophagocytosis describes the pathological finding of activated macrophages, engulfing erythrocytes (red blood cells), leukocytes (white blood cells), platelets, and their precursor cells. This phenomenon is an important finding in patients with hemophagocytic syndrome, more properly referred to as hemophagocytic lymphohistiocytosis (HLH). A familial form of the disease (now referred to as familial hemophagocytic lymphohistiocytosis) also has been identified.

Breeds at Risk

Histiocytic disorders of dogs include histiocytoma, localized histiocytic sarcoma (HS), disseminated HS (malignant histiocytosis ), and the reactive histiocytoses: cutaneous and systemic. Breeds affected include Bernese Mountain Dog, Golden Retriever, Rottweiler, Labrador Retriever, Schnauzer, and Tibetan Terrier.

Clinical Signs of Hemophagocytic Syndrome

Clinical signs associated with hemophagocytic syndrome include fever, jaundice, enlarged spleen and liver, and diarrhea. Of central nervous system manifestations, seizures are the most commonly reported.

Management and Prognosis for Hemophagocytic Syndrome

Overall, dogs with infection-associated hemophagocytic syndrome have better 1-month survival rates than dogs with immune-associated and idiopathic hemophagocytic syndrome. Therapy is dictated by the underlying diagnosis.

HLH has since been associated with a variety of viral, bacterial, fungal, and parasitic infections, such as Lyme disease. Hemophagocytic syndrome of any cause is potentially life-threatening.