The hypereosinophilic syndrome is a disease characterized by a persistently
elevated eosinophil count in the blood for at least six months without any
recognizable cause, with involvement of either the heart, nervous system, or
bone marrow. HES is a diagnosis of exclusion, after
clonal eosinophilia and reactive eosinophilia have been ruled out.
There are some associations with chronic eosinophilic leukemia as it shows
similar characteristics and genetic defects.
If left untreated, HES is progressively fatal. It is treated with
glucocorticoids such as prednisone. The addition of the monoclonal antibody
mepolizumab may reduce the dose of glucocorticoids.
Classification In the heart, there are two forms of the
hypereosinophilic syndrome, endomyocardial fibrosis and Loeffler's
endocarditis. Endomyocardial fibrosis is seen in
tropical areas. Loeffler's endocarditis does not have
any geographic predisposition. Signs and symptoms
As HES affects many organs at the same time, symptoms may be numerous. Some
possible symptoms a patient may present with include:
Cardiomyopathy Skin lesions
Thromboembolic disease Pulmonary disease
Neuropathy Hepatosplenomegaly
Reduced ventricular size Diagnosis
Numerous techniques are used to diagnose hypereosinophilic syndrome, of which the
most important is blood testing. In HES, the eosinophil count is greater than 1.5
× 109/L. On some smears the eosinophils may appear normal in appearance, but
morphologic abnormalities, such as a lowering of granule numbers and size,
can be observed. Roughly 50% of patients with HES also have anaemia.
Secondly, various imaging and diagnostic technological methods are utilised to
detect defects to the heart and other organs, such as valvular dysfunction and
arrhythmias by usage of echocardiography. Chest radiographs may
indicate pleural effusions and/or fibrosis, and neurological tests such as
CT scans can show strokes and increased cerebrospinal fluid pressure.
A proportion of patients have a mutation involving the PDGFRA and FIP1L1 genes on
the fourth chromosome, leading to a tyrosine kinase fusion protein. Testing
for this mutation is now routine practice, as its presence indicates
response to imatinib, a tyrosine kinase inhibitor.
Treatment Treatment primarily consists of reducing
eosinophil levels and preventing further damage to organs. Corticosteroids, such
as Prednisone, are good for reducing eosinophil levels and antineoplastics
are useful for slowing eosinophil production. Surgical therapy is rarely
utilised, however splenectomy can reduce the pain due to spleen enlargement. If
damage to the heart, then prosthetic valves can replace the current organic
ones. Follow-up care is vital for the survival of the patient, as such the
patient should be checked for any signs of deterioration regularly. After
promising results in drug trials it is hoped that in the future
hypereosinophilic syndrome, and diseases related to eosinophils such as asthma
and Churg-Strauss syndrome, may be treated with the monoclonal antibody
Mepolizumab currently being developed to treat the disease. If this becomes
successful, it may be possible for corticosteroids to be eradicated and
thus reduce the amount of side effects encountered.
Epidemiology HES is very rare, with only 50 cases
being noted and followed up in the United States between 1971 and 1982,
corresponding roughly to a prevalence of 1 to 2 per million people. The disease
is even more uncommon within the paediatric population.
Patients who lack chronic heart failure and those who respond well to Prednisone
or a similar drug have a good prognosis. However, the mortality rate rises in
patients with anaemia, chromosomal abnormalities or a very high white blood
cell count. References
External links DermNet systemic/hypereosinophilic
Hypereosinophilic Syndrome research in UK
Hypereosinophilic Syndrome on patient.info
Hypereosinophilic Syndrome on eMedicine Hypereosinophilic Syndrome on American
Academy of Allergy, Asthma & Immunology Hypereosinophilic syndrome on Mayo
Clinic