IgE myeloma is a rare variant of multiple myeloma, characterized by the neoplastic proliferation of plasma cells that produce immunoglobulin E (IgE).
IgE myeloma was first described in 1967 by Johansson and Bennich and till date, only 40 cases have been documented [1] [2] [3]. IgE myeloma does not present with any specific symptoms or signs when compared to the other forms of multiple myeloma (MM) [4]. It is, however, considered to be a more aggressive entity, with studies showing the median survival time to be reduced (16 months vs 30 months for other types of MM) [5] [6].
The average age of onset of this disease is 62 years, ranging from 38-80 years. It is known to occur slightly more commonly in males. Patients usually present in a similar manner to other forms of MM, with bone pain, anemia, hypercalcemia and renal failure forming the clinical spectrum.
The most common complaint of patients is bone pain, occurring in the lumbar areas. Other areas that may be involved are the long bones, the skull, and pelvis. They may be associated with pathological fractures, mostly involving the axial skeleton. Spinal cord compression may be a result of these compressive, osteolytic bone lesions.
Anemia may present as weakness in a majority of patients. The incidence of hepatosplenomegaly is higher in IgE myeloma, as compared to the commoner variants of MM [7].
Hypercalcemia, seen in almost 30% of patients, may present as nausea, constipation, thirst, somnolence and confusion. Renal insufficiency, a marker of poor prognosis, may be seen in a few patients [8].
Patients may also report certain constitutional symptoms related to hyperviscosity. An increased incidence of infections may also be found in such patients.
IgE myeloma is to be suspected in middle-aged adults who present with the characteristic symptoms of bone pain, along with the other features, or in those who have incidental abnormalities on routine blood tests, including anemia, raised erythrocyte sedimentation rate (ESR) or hypercalcemia [9].
Routine blood tests to be done include a complete blood count (CBC) that demonstrates a normocytic normochromic anemia, present in roughly three-quarters of patients. WBC and platelet counts are usually unaffected. ESR may be raised to > 100 mm/hr.
Hypercalcemia may be present in 10% of patients at the time of diagnosis. Other renal function tests like serum creatinine, blood urea nitrogen test (BUN) and serum uric acid may reveal features of renal insufficiency.
In contrast to the other variants of multiple myeloma, most patients with IgE myeloma do not demonstrate monoclonal protein bands on serum or urine electrophoresis. The diagnosis is then made by bone marrow aspiration and biopsy, that may reveal large numbers of plasma cells. Immunohistochemical staining will show these plasma cells to be strongly positive for IgE in their cytoplasm. Light chain analysis may have prognostic significance in these patients [10].
Imaging might reveal the characteristic pathological fractures or lytic lesions in the skeleton and hence, plain X-rays of the spine, skull, pelvis and long bones need to be carried out. Magnetic resonance imaging (MRI) may help localize the site of bone pain. Positron emission tomography (PET) scans are rarely required.
Chromosomal studies may be done to detect the characteristic translocation abnormalities seen in IgE myeloma.