Clonality of Isolated Eosinophils in the Hypereosinophilic Syndrome

Abstract

The idiopathic hypereosinophilic syndrome (IHES) is a rare disorder characterized by unexplained, persistent eosinophilia associated with multiple organ dysfunction due to eosinophilic tissue infiltration. In the absence of karyotypic abnormalities, there is no specific test to detect clonal eosinophilia in IHES. Analysis of X-chromosome inactivation patterns can be used to determine whether proliferative disorders are clonal in origin. Methylation of HpaII andHha I sites near the polymorphic trinucleotide repeat of the human androgen receptor gene (HUMARA) has been shown to correlate with X-inactivation. In this study, we have used the polymerase chain reaction (PCR) with nested primers to analyze X-inactivation patterns of the HUMARA loci in purified eosinophils from female patients with eosinophilia. Peripheral blood eosinophils were isolated by their autofluoresence using flow cytometric sorting. Eosinophils purified from a female patient presenting with IHES were found to show a clonal pattern of X-inactivation. Eosinophil-depleted leukocytes from this patient were polyclonal by HUMARA analysis, thus excluding skewedness of random X-inactivation. After corticosteroid suppression of her blood eosinophilia, a clonal population of eosinophils could no longer be detected in purified eosinophils. In contrast, eosinophils purified from a patient with Churg-Strauss syndrome and from six patients with reactive eosinophilias attributed to allergy, parasitic infection, or drug reaction showed a polyclonal pattern of X-inactivation by HUMARA analysis. The finding of clonal eosinophilia in a patient presenting with IHES indicates that such patients may have, in reality, a low-grade clonal disorder that can be distinguished from reactive eosinophilias by HUMARA analysis. Further, the method described can be used to monitor disease progression.

Eosinophilic pneumonias

“…The historical definition of the ‘idiopathic’ HES proposed by Chusid et al in 1975 (94) empirically included: 1) a persistent eosinophilia >1.5 × 10 9 /l for longer than 6 months, or death before 6 months associated with the signs and symptoms of hypereosinophilic disease, 2) a lack of evidence for parasitic, allergic or other known causes of eosinophilia, and 3) presumptive signs and symptoms of organ involvement, including hepatosplenomegaly, organic heart murmur, congestive heart failure, diffuse or focal central nervous system abnormalities, pulmonary fibrosis, fever, weight loss or anaemia. Recent studies have demonstrated that the so‐called HES represents indeed a considerably heterogeneous group of disorders, that may result especially from clonal proliferation of lymphocytes or of the eosinophils themselves (95–100).…”

Blood Eosinophilia: A New Paradigm in Disease Classification, Diagnosis, and Treatment

“…This contention was supported by clonality studies that used X-linked DNA analysis. 92 In contrast, the presence of clonal T H 2 lymphocytes in a subset of patients with "HES" suggests a pathogenetic heterogeneity that may include an IL-5-mediated secondary eosinophilia in the mix. 93,94 In a study of 60 patients with HES, 16 (27%) had T cells with an aberrant immunophenotype, and T-cell clonality was suggested in half of these 16 patients.…”

Hypereosinophilic Syndrome: Lymphoproliferative and Myeloproliferative Variants

“…A few reports did provide support for a primitive myeloid disorder by showing chromosomal abnormalities adjacent to eosinophil granules 14 or skewed methylation patterns of Xlinked genes in purified granulocytes or eosinophils. 15,16 Unfortunately, applicability of these methods in HES is limited, as abnormal karyotypes are rare in this disorder, and X-linked polymorphisms can be investigated only in female patients, in the setting of a disease that predominantly affects males.…”