Overproduction of White Blood Cells in the Bone Marrow in Dogs

Eosinophils are a type of white blood cells which are produced in bone marrow. Hypereosinophilic syndrome is a condition in which there is a higher than normal number of osinophils ( white blood cells) present in the circulating blood. This condition is characterized by persistent eosinophilia – sustained overproduction of eosinophilis in the bone marrow. 

Definitive cause of this disorder is not known however it is suspected that hypereosinophilic syndrome occurs in response to an unidentified antigen or impairment of the immune response and control of eosinophilis production. This multi-system syndorme affects various tissues, thereby causing inflammations and eventual damage of organs. The outcome is frequently fatal.

Organ damage due to hypereosinophilic syndrome occurs due to the effect of eosinophil granule products and eosinophil-derived cytokines, a category of regulatory proteins that are released by cells in the immune system into the tissues.

Common organs that are affected by this syndrome include  gastrointestinal tract (especially the intestine and liver), spleen, bone marrow, lungs, and lymph nodes (especially those in the abdominal area). Less commonly affected sites are skin, kidney, heart, thyroid, adrenal glands and pancreas.

This is a rare disorder but Rottweilers are thought to be predisposed to this syndrome.

As Hypereosinophilic Syndrome can affect different organs simultaneously, numerous types of symptoms might occur. The nature of the symptoms depends on the organ or body part that gets affected by this condition. Common signs and symptoms associated with hypereosinophilic syndrome include



Loss of appetite (anorexia)

Intermittent vomiting and diarrhea

Weight loss


Enlargement of the liver and spleen

Thickened (diffuse or segmental) intestine that is non-painful

Abdominal masses

Itching and seizures (less frequently)

Mesenteric and possibly peripheral lymphadenopathy (swollen lymph nodes in the abdominal region or other areas of the body)

Mass lesions caused by eosinophilic granulomatous (inflamed masses of tissue) involving the lymph nodes and/or organs

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