Histiocytosis in Dogs

Overview of Canine Histiocytosis

Histiocytosis is a disorder that can occur in dogs resulting from the proliferation or multiplication of cells from the cells that are involved in the inflammatory response, which are the monocyte-macrophage line.

There are two types of histiocytosis:

• Systemic histiocytosis – a nonmalignant (not cancerous) disorder
• Malignant histiocytosis – a malignant (cancerous) disorder

The cause of histiocytosis is unknown though it is thought to be hereditary. Middle aged male dogs and Bernese mountain dogs seem to be predisposed to developing systemic histiocytosis. Older dogs tend to develop malignant histiocytosis. Breeds prone to malignant histiocytosis include Bernese mountain dogs, Rottweilers, Doberman pinschers, Labrador retrievers, flat-coated retrievers and golden retrievers.

What to Watch For

Signs seen common to both types of histiocytosis including:

• Lethargy
• Anorexia
• Weight loss
• Respiratory noise
• Coughing
• Dyspnea (difficulty breathing)
• Enlarged lymph nodes
• Abdominal enlargement

In patients with systemic histiocytosis watch for skin lesions or masses and ocular (eye) changes of any sort.

In patients with malignant histiocytosis watch for pale mucous membranes, weakness, neurologic signs, and severe respiratory signs

Diagnosis of Histiocytosis in Dogs

• Baseline tests to include a complete blood count (CBC), biochemical profile, and urinalysis are recommended in all patients. Different degrees of anemia (low red blood cell count) and thrombocytopenia (low platelet count) are usually seen. Changes in the profile usually represent the degree and type of organ involvement.
• Radiographs (X-rays) of the thorax (chest) and abdomen are recommended, as changes in the lungs and abdominal cavity are not uncommon.
• Bone marrow aspirate for cytology (cell evaluation) is helpful.
• Affected organ and/or lymph node biopsy is often diagnostic.

Treatment of Histiocytosis in Dogs

There is no definitive treatment for histiocytosis, and prognosis, especially the malignant form, is poor. Your veterinarian may recommend the following for your dog:

• Fluid and electrolyte therapy in those patients who are dehydrated
• Blood and plasma transfusions to support those patients that are profoundly anemic or hypoproteinemic (have low protein levels)
• Certain types of chemotherapy

Home Care and Prevention

Administer all medication and diet as directed by your veterinarian. If any change is noted in your dog’s condition, notify your veterinarian.

Return for follow up examination and testing as recommended by your veterinarian.

There is no prevention for histiocytosis.