Hecksel, Kathleen A.

Abstract BACKGROUND: The molecular etiology of idiopathic acquired sideroblastic anemia (IASA), now considered a form of myelodysplastic syndrome, is currently unknown. Romslo et al (Blood 1982) reported a patient with IASA who had moderately elevated free erythrocytic protoporphyrin (FEP); this observation is now frequently made in IASA, helping distinguish IASA (high FEP) from inherited sideroblastosis (low FEP). In addition, rare patients with erythropoietic protoporphyria (EPP)—defined by cutaneous photosensitivity, dramatically elevated FEP levels, and germline point mutations in the ferrochelatase (FECH) gene at 18q21.3—have ringed sideroblasts in their marrow. We hypothesized that patients with IASA might have acquired somatic FECH mutations. METHODS AND RESULTS: We designed a denaturing high performance liquid chromatography (DHPLC) assay to explore this possibility and to avoid problems related to mutation screening in the setting of mixed clonality. To validate the DHPLC assay, the coding region of the FECH gene from 2 molecularly undiagnosed EPP patients without liver disease was analyzed. In one patient, both a heterozygous 69delG mutation (GenBank Accession NM_000140) and heterozygosity for the FECH expression-modulating IVS3-48C/T polymorphism were detected. In the other patient, no FECH coding mutations or polymorphisms were detected, either by DHPLC or conventional dye sequencing. FEP measurements were then obtained on 2 IASA patients and were elevated (65 and 115 mcg/dL; normal 1–10 mcg/dL) with normal urine and fecal porphyrins. Genomic DNA obtained from these 2 patients as well as archival DNA from 30 other patients with IASA was amplified and tested for FECH mutations. No coding region mutations were detected. Synonymous polymorphisms in exon 7 (rs536765) and 9 (rs536560) were found in 6/32 (19%; normal heterozygosity 0.398) and 14/32 (44%; normal heterozygosity 0.402) samples, respectively. The IVS3-48C/T polymorphism (rs2272783) was found in 3/32 (9%) (prevalence in the general population is 11%, Gouya Nat Genet 2002). In addition, 3 intronic polymorphisms not in the refSNP database were detected: IVS8+34 C/T (2/32), IVS8-61delG (5/32), and IVS9-59delA (2/32). CONCLUSION: IASA is not associated with coding mutations in FECH. Elevation of FEP in ASA must instead be due to the lack of mitochondrial iron in the proper form for incorporation into the porphyrin ring; attention should instead focus on factors responsible for maintaining the appropriate redox state and compartmentalization of iron. DHPLC can detect FECH mutations and polymorphisms, but because of the high frequency of the latter and the consequent need to sequence multiple exons, it is not a practical screening tool for studying undiagnosed EPP patients.

Abstract Introduction: Primary systemic amyloidosis occurs when a clonal plasma cell population secretes light chains (or light chain fragments) that deposit in tissues as amyloid and cause organ failure and ultimately patient death. Primary systemic amyloidosis generally results from non-proliferative small populations of plasma cells. While it is known that IgG, IgA and light chain producing plasma cells can secrete amyloid in association with myeloma, fewer medical professionals recognize that IgM-secreting lymphoplasmacytic cells can produce amyloid proteins. When monoclonal IgM secreting marrow lymphocytes are present, amyloidosis can result with or without overt Waldenstrom Macroglobulinemia. Patients and Methods: All patients seen at the Mayo Clinic between January 1968 and August 2000 with both a serum IgM monoclonal protein and biopsy-proven amyloidosis were analyzed. The Mayo Clinic Dysproteinemia Database recognized 128 patients (42 female, 86 male) with a median age of 65 years. Results: Seventy-two percent (n=92) of the patients have died with a median survival of 1.72 years following biopsy proven amyloidosis (figure 1). Median serum IgM monoclonal spike was 1.38 g/dL. In addition, serum IgM kappa to lambda light chain ratios (1:3) were found to be reversed in patients with IgM gammopathy when amyloid was present (compared to the reverse ratio (3:1) in patients with Waldenstrom macroglobulinemia in the absence of amyloidosis). Subcutaneous fat, rectum and bone marrow revealed amyloid in 72%, 69% and 70%, respectively, providing non-invasive techniques for amyloidosis diagnosis without the risks of bleeding associated with renal or hepatic percutaneous biopsy. Variables not shown to affect survival included the following: age, gender, serum M spike, urine protein, alkaline phosphatase, creatinine, light chain isotype, ejection fraction, and percent marrow plasma cells. The presence of amyloid cardiomyopathy (defined as a cardiac interventricular septal thickness greater than 12 mm.) was the only variable to adversely affect survival. Of the patients with echocardiographic evidence of cardiomyopathy, the median survival was 10.8 months. In contrast, the patients without echocardiographic evidence of cardiomyopathy at diagnosis had a median survival of 39 months (figure 2). Conclusion: Amyloidosis is underappreciated and should be considered in the differential diagnosis of all patients presenting with IgM gammopathy. Patients found to have amyloidosis in this setting should be tested for amyloid cardiomyopathy, as its presence predicts poor outcome. Lambda light chain in serum IgM samples should increase the index of suspicion for the presence of amyloid since IgM lambda is present in only 25% of IgM MGUS or Macroglobulinemia patients but is seen in 75% of IgM amyloidosis patients. Figure Figure