Histiocytosis

What is Histiocytosis?
Histiocytosis encompasses a wide range of cancers associated with histiocytes, a type of white blood cell. The disorders range from benign skin growths called histiocytomas that usually go away by themselves to a fatal disorder called malignant histiocytosis (disseminated histiocytic sarcoma). The latter is an aggressive cancer that may infiltrate the spleen, liver, lungs, bone marrow and lymph glands.  An intermediate type, called systemic histiocytosis, is benign but tumors may be widespread and may recur.

How does my dog get Histiocytosis?
The exact cause is not known, but malignant histiocytosis is considered to be inherited in Bernese Mountain Dogs as a polygenic trait, meaning it is controlled by the combined activity of several genes. 

How do I know if my dog has Histiocytosis?
Signs of systemic and disseminated histiocytosis include lethargy, appetite and weight loss, and sometimes coughing and difficulty breathing. Systemic histiocytosis usually occurs in young to middle aged dogs. Early signs are skin tumors, particularly on the face and limbs. Tumors may occur in the lungs, causing difficulty breathing. The eyes may be affected, so they may be reddened or painful. Malignant histiocytosis usually occurs in older dogs, especially Bernese Mountain Dogs. Affected dogs may be weak, with pale mucous membranes, and may have difficulty breathing. The eyes and skin are usually not involved. Your veterinarian will perform a complete examination, as well as blood tests, radiographs of the chest and abdomen to look for tumors or enlarged organs, and possibly biopsies of tumors or lymph nodes.

What can I do about Histiocytosis?
Treatment depends on the type of histiocytosis. For systemic histiocytosis, your veterinarian may prescribe corticosteroids to reduce inflammation. Immunosuppressive drugs may be tried. You may have to keep your dog on medication indefinitely, as recurrences are very common. For disseminated histiocytosis, your veterinarian may prescribe corticosteroids or chemotherapy drugs, which may help. Unfortunately, no therapy has been found to be successful long term, and most dogs do not survive more than a few months.

Is there anything I can do to prevent my dog from getting Histiocytosis?
Avoid breeding affected dogs, and avoid buying a puppy from a family with affected dogs.

Are there certain breeds that get  Histiocytosis more often?
Bernese Mountain Dogs and Flat Coated Retrievers have the highest incidence. It has also been reported in Golden Retrievers and Labrador Retrievers.