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Chronic Myeloid Neoplasms

Myeloproliferative neoplasms (MPN)

Hypereosinophilic syndrome

Reviewer: Nikhil Sangle, M.D. (see Reviewers page)
Revised: 30 September 2014, last major update August 2011
Copyright: (c) 2001-2014, PathologyOutlines.com, Inc.


● Diagnosis of exclusion; also called idiopathic hypereosinophilic syndrome
● See also discussions in these chapters: Gallbladder-eosinophilic cholecystitis, Lung-nontumor: eosinophilic pneumonia, Pancreas-eosinophilic pancreatitis
● Much rarer than reactive eosinophilia
Note: published cases without molecular analysis may be chronic eosinophilic leukemia, hypereosinophilic syndrome, myeloid neoplasms associated with eosinophilia and abnormalities of PDGFRA, PDGFRB, or FGFR1, T-cell lymphoproliferative disorder or mast cell disease (with eosinophilia)


● Bone marrow examination with tryptase (to detect mast cells), T cell clonality studies, immunohistochemistry, cytogenetic studies and molecular studies to detect (and rule out) PDGFRA, PDGFRB or FGFR1

Diagnostic criteria:
● ≥ 1.5 x 109/L peripheral blood eosinophils (persisting for >6 months), exclusion of secondary eosinophilia by appropriate thorough investigation(s), exclusion of other acute or chronic myeloid neoplasms, myelodysplastic syndrome and mast cell disorder, no evidence for phenotypically abnormal or clonal T lymphocytes, no cytogenetic abnormality, < 2% peripheral blasts and < 5% bone marrow blasts
Note: some studies add criterion of no evidence of clonality, which may be difficult to determine if no cytogenetic abnormalities are present - Diagnostic algorithm (WHO 2008)

Case reports of organ/tissue involvement

● Cardiac (Pathol Int 2008;58:138, Am J Hematol 2007;82:920)
● CSF (Surg Neurol 2007;68 Suppl 1:S52)
● Liver (Intern Med 2007;46:1095)
● Oral mucosa (Oral Dis 2008;14:115)
● Venous disease (Arch Dermatol 2006;142:1606)


● Immediate therapy may not be required if asymptomatic and no organ damage
● Cytoreductive therapy includes corticosteroids, interferon-alpha and hydroxyurea (Cancer J 2007;13:384)

Micro description

Bone marrow: hypercellular marrow, increased eosinophilic precursors

Micro images

From cases before molecular studies were indicated

Peripheral blood:

Three eosinophils show marked hypogranulation in 50 year old man with 3 year history of hypereosinophilic syndrome with progressive marrow failure and multiple organ involvement

Reactive eosinophilia (for comparison) shows normal number and size of granules, occasional vacuoles, and slightly hyperlobulated nuclei (eosinophilia had no identifiable cause, gradually resolved)

Bone marrow smear:

50 year old patient (above) has marked increase in eosinophils at all levels of maturation, some granules are basophilic and some eosinophilic myelocytes have reduced granules

Additional references

eMedicine #1, #2, Orphanet

End of Chronic Myeloid Neoplasms > Myeloproliferative neoplasms (MPN) > Hypereosinophilic syndrome

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