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sideroblastic anemia
A group of disorders characterized by ringed sideroblasts in nucleated erythroid precursors in the marrow.
Etiology:
1) hereditary
- rare, sex-linked hereditary defect of gamma-aminolevulinic acid synthase
2) acquired:
a) refractory anemia with ringed sideroblasts
b) heavy alcohol ingestion
c) pharmaceutical agents
1] anticonvulsants
2] isoniazid
d) nutritional/toxins
1] excess zinc intake
2] copper deficiency
3] lead poisoning
Pathology:
1) >10% of normoblasts contain iron-laden mitochondria that surround the nucleus & appear as pathognomonic rings when stained with Prussian blue
2) the final step in heme synthesis (insertion of iron) occurs in the mitochondria
3) iron overload in hereditary form may be severe
Laboratory:
1) complete blood count
a) anemia
b) RDW is often increased
c) MCV & MCHC are reduced
d) RBC count is decreased
2) peripheral smear
a) hypochromic, microcytic anemia
b) often shows dimorphic population of erythrocytes
c) macrocytic erythrocytes with basophilic stippling that stain positive for iron [2]*
3) serum iron levels are elevated
4) % transferrin saturation is generally high (30-80%)
5) serum ferritin levels are generally elevated (50-300 ug/L)
6) bone marrow biopsy
* MKSAP17 classifies sideroblastic anemia as macrocytic anemia
Management:
1) pyridoxine 100-200 mg PO QD
a) hereditary forms often respond
b) acquired forms less frequently respond
2) stop offending agents
Interactions
disease interactions
Related
aminolevulinic acid [ALA] synthetase
heme synthesis
Specific
acquired idiopathic sideroblastic anemia
refractory anemia with ringed sideroblasts (RARS)
sideroblastic anemia with spinocerebellar ataxia
X-linked sideroblastic anemia
General
bone marrow disease
hypochromic anemia
hypoplastic anemia
macrocytic anemia
References
- Harrison's Principles of Internal Medicine, 13th ed.
Isselbacher et al (eds), McGraw-Hill Inc. NY,
1994, pg 1725
- Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 17.
American College of Physicians, Philadelphia 1998, 2012, 2015
- Harrison's Principles of Internal Medicine, 14th ed.
Fauci et al (eds), McGraw-Hill Inc. NY, 1998, pg 643, 2157