Chronic Myeloid Neoplasms - Refractory anemia with ringed sideroblasts

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Chronic Myeloid Neoplasms

Myelodysplastic syndromes

Refractory anemia with ringed sideroblasts

Reviewer: Nikhil Sangle, M.D. (see Reviewers page)
Revised: 12 August 2011, last major update August 2011
Copyright: (c) 2001-2011, PathologyOutlines.com, Inc.

Definition
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● Also called idiopathic acquired sideroblastic anemia

Laboratory
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● Commonly normochromic macrocytic or normochromic normocytic anemia (hemoglobin usually is <10 g/dL), usually no other cytopenias but rarely may have thrombocytosis

Diagnosis
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● Ringed sideroblasts detected with iron (Prussian-blue) stain represent at least 15% of bone marrow erythroblasts
● Iron accumulates in mitochondria of erythroid precursors

Case reports
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● 16 year old girl with hypochromic microcytic anemia (Arch Pathol Lab Med 2005;129:e199)

Micro description
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● Peripheral blood: two RBC populations-normal and microcytic hypochromic; occasional coarse basophilic stippling and Pappenheimer bodies; no dysplastic changes, minimal neutropenia, no myeloblasts, no monocytosis, no thrombocytopenia
● Bone marrow-general: hypercellular or normocellular marrow with erythroid hyperplasia
● Bone marrow-erythroid: erythroid hyperplasia, may be mild to moderate dysplasia; markedly increased iron stores, ringed sideroblasts ≥15% of marrow erythroblasts, identify with iron stain on marrow smear, has nucleus completely or partially (at least one third circumference) encircled by iron granules
● Bone marrow-myeloid: myeloblasts <5% (or call RAEB), no dysplasia
● Bone marrow-megakaryocytes: no dysplasia

Micro images
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Peripheral blood:

Red blood cells are dimorphic with normochromic and markedly hypochromic cells

Bone marrow smear:

Prussian blue stain shows most red blood cell precursors are encircled by small granules of iron

RARS with thrombocythemia

Fig 1: peripheral blood shows dual population of microcytic and normocytic red cells with marked poikilocytosis
Fig 2: bone marrow smear shows marked erythroid hyperplasia with many erythroid precursors having megaloblastoid maturation or nucleocytoplasmic asynchrony
Fig 3: iron stain shows numerous ringed sideroblasts (perinuclear iron granules encircle more than 1/3 of nuclear circumference)
Fig 4: transmission EM shows nonspecific siderosomes (black arrow) and iron-laden mitochondria (white arrow)

Electron microscopy description
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● Perinuclear iron present in mitochondrial cristae

EM images
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Erythroid precursor shows iron deposits in mitochondrial cristae

Molecular
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● No specific cytogenetic abnormality (Atlas of Genetics and Cytogenetics)
● Clonal cytogenetic abnormalities involve a single chromosome in 15–20% cases (Leuk Res 2006;30:178)
● JAK2-V617F mutation present in 48-67% with RARS and marked thrombocytosis (RARS-T), a provisional MDS/MPN disorder (Haematologica 2008;93:34, Blood 2006;108:2173)

Differential diagnosis
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● Refractory cytopenia with multilineage dysplasia: may have 15%+ ringed sideroblasts, but also dysplastic changes in 2 or 3 lineages
● Congenital (hereditary x-linked) sideroblastic anemia: causes decrease in the end product of porphyrin synthesis (protoporphyrin IX)
● Chloramphenicol or TB drug (isoniazid) exposure, copper deficiency, alcohol or chronic lead poisoning, excess zinc administration

End of Chronic Myeloid Neoplasms > Myelodysplastic syndromes > Refractory anemia with ringed sideroblasts

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