Malignant Histiocytosis, also sometimes called Disseminated Histiocytic Sarcoma, is a relatively rare disease that is usually fatal. This disorder involves white blood cells that infiltrate a variety of organs, causing them to fail and the life expectancy can be anywhere from hours to weeks after diagnosis. Even more frustrating, this disease can be very difficult to diagnose. In this article, we'll learn how Malignant Histiocytosis develops, its symptoms and what options are available for those that are suffering from this disease.

What is Malignant Histiocytosis?

Histiocytes are a kind of white blood cell that derives from the bone marrow. Their purpose is to latch on to material that should not be in the body and dispose of them. From the bone marrow, they travel to different organs in the body to help keep them healthy. Dogs that have Malignant Histiocytosis have too many histiocytes in their bodies, which can then accumulate in certain areas and form tumors. Malignant Histiocytosis is the most aggressive of the histiocytic disorders, as many tumors can form at the same time. Malignant Histiocytosis very commonly metastasizes to the lungs, forming multiple tumors, and can also be found in the spleen, lymph nodes, liver and bone marrow.

Which dogs are affected?

This rare disease usually affects Bernese Mountain Dogs, Golden Retrievers, Flat-Coated Retrievers and Rottweilers, although it has been seen from time to time in other breeds. Little is known about what causes the disease to develop, but there is evidence to suggest that the disease is inherited. It is highly recommended that dogs that develop this disorder not be bred, but because dogs have usually reached middle age before the disease develops, they have often already been bred.

What are the symptoms?

Symptoms for Malignant Histiocytosis can include recurrent fevers, loss of appetite, depression, and in some cases, seizures or difficulty in using the rear limbs. Because the disease often develops in the lungs, difficulty breathing or coughing may occur as well.

Diagnosis and Treatment

Unfortunately, Malignant Histiocytosis is a very difficult disease to diagnose, not in the least because it is so rare. It is often confused with Histiocytic Sarcoma, which is when the disease is only present in one area of the body, and is not fatal if the tumor can be removed. If tumors are present in the lungs, they can be seen on an x-ray. The best way to diagnose the disease is to perform a biopsy, which will also help give clues to how far the disease has progressed and how best to treat it.

Unfortunately, there is no cure for Malignant Histiocytosis, and because it moves so quickly, the disease can be very well developed before it is even diagnosed. The life expectancy for a dog diagnosed with Malignant Histiocytosis can be hours or weeks. While chemotherapy has been used in order to combat the disease, it only works to prolong the inevitable. The only treatment available is to work as a team with the veterinarian to make the dog as comfortable as possible until the quality of life fades.