1. Sideroblastic anemias are a group of refractory anemias characterized by ring sideroblasts in the bone marrow, which are iron-containing erythroblasts. 2. Hereditary sideroblastic anemias are rare, often manifesting in males in childhood or adolescence. They can be caused by mutations in genes involved in iron-sulfur cluster formation or heme synthesis. 3. Acquired sideroblastic anemias have various causes including drugs, toxins, myelodysplastic syndromes, and other hematological malignancies.

1. DISORDERS OF HAEM
SYNTHESIS

2. Porphyrias
Lead Poisoning
Sideroblastic Anaemia

3. Structure of Haem

4. • Ferrous iron (Fe++)
• Protoporphyrin IX:
contains 4 pyrrole
rings linked together
by methenyl bridges.

5. HAEM SYNTHESIS
• 85% haem synthesis occurs in red cell
precursors.
• Reticulocytes continue to synthesize
haemoglobin for 24-48hrs after release
from bone marrow.
• Ceases when RBC’s mature because they
lack mitochondria.
• Liver is the main non-RBC source of
haem synthesis.

6. • 80% transferrin iron normally enters developing red
cells for haem synthesis.
• Transferrin-receptor complex taken up into
mitochondria by endocytosis.
• Iron released at low pH of endosome via DMT1 &
reduced from Fe+++ to Fe++ by STEAP3, a
ferrireductase.
• Transported into mitochondria by mitoferrin or
enters ferritin.

7. Iron uptake by developing red cell

8. HAEM SYNTHESIS
Mitochondrion Cytoplasm
Succinyl-CoA ALA-dehydrogenase
δ ALA-synthase
+ Pyridoxal phosphate
δ-Amino
Porphobilinogen
laevulinic acid
Glycine
PBG-deaminase
Hydroxymethylbilane
Haem
Uro’gen III synthase
Ferrochelatase
Uroporphyrinogen III
Protoporphyrin IX
Proto’gen III oxidase
Uro’gen III decarboxylase
Protoporphyrinogen III Copro’gen III oxidase Coproporphyrinogen III

10. Coordination of haem synthesis, globin
synthesis & iron regulation.

11. • Reduced levels of haem rapidly trigger
formation of haem-regulated
inhibitor(HRI).
• HRI interacts with translation initiating
factor eIF-2α & prevents translation of
α & β chains.

12. PORPHYRIAS
• Group of inherited or acquired diseases.
• Each characterized by a partial defect
in one of the enzymes of haem
synthesis.
• Classified into two groups: Hepatic &
Erythropoietic.

13. Hepatic Porphyrias
FORM ENZYME DEFECT
• Acute intermittent • Porphobilinogen
porphyria deaminase (PBG)
• Hereditary • Coproporphyrinogen
coproporphyria oxidase
• Porphyria variegate • Protoporphyrinogen
oxidase
• Porphyria cutanea tarda • Uroporphyrinogen
(PCT) decarboxylase

14. Erythropoietic Porphyrias
FORM ENZYME DEFECT
• Congenital • Uroporphyrinogen
erythropoietic porphyria oxidase
• Erythropoietic • Ferrochelatase
protoporphyria

15. Congenital Erythropoietic Porphyria
• Rare autosomal recessive disorder.
• Reduced uroporphyrinogen III synthase activity d/t
mutations in the encoding gene.
• Males/females equally effected.
• Age of onset is variable but typically seen in infants &
children.

16. Clinical presentation:
• Highly variable.
• Characterized by cutaneous photosensitivity &
dermatitis (ranging from mild to severe).
• Spontaneous oxidation of accumulated porphyrinogens
to photoactive porphyrins.
• Hemolytic anaemia, may be mild to severe with
resultant splenomegaly & osseous fragility.

17. • Hypertrichosis
• Port-wine coloured urine
• Hydrops fetalis
• Blepharitis, conjunctivitis, corneal scarring &
blindness.
• Inc. amounts of uroporphyrin &
coproporphyrin in bone marrow, red
cells, plasma, urine & faeces.

18. Management:
• Avoidance of sunlight
• Splenectomy (to improve red cell survival) is only
partially effective.
• High level blood transfusions & iron chelation therapy
(to suppress erythropoiesis) sufficiently improve
symptoms.
• Allogeneic bone marrow transplantation has been
successful.

19. Erythropoietic Protoporphyria
• Autosomal dominant disorder.
• Deficiency of ferrochelatase enzyme d/t mutations in
the encoding gene.
• Males/females equally effected.
• Onset is usually in childhood.

20. • Inc. protoporphyrin concentrations in bone
marrow, red cells, plasma & bile.
• Bone marrow reticulocytes are primary source of
excess protoporphyrin.
• Photosensitivity & dermatitis range from mild or
absent to severe.
• Little haemolysis but mild hypochromic anaemia may
occur.
• Occasionally severe liver disease may occur.

21. • Urinary porphyrin levels are normal in patients
without liver dysfunction.
• Management:
• Avoid sunlight.
• Beta-carotene may also diminish photosensitivity.
• Iron deficiency should be avoided as this may inc.
amount of free protoporphyrin.

22. Porphyria Cutanea Tarda (PCT)
• Most common hepatic porphyria.
• Type I (acquired) - 80%
• Type II (autosomal dominant)
• Dec. activity of uroporphyrinogen decarboxylase
(UROD)
• More common in men.
• Precipitated in middle or later life by factors like
alcohol, liver disease or estrogen therapy.

23. • Inc. amounts of uroporphyrins & carboxyl-porphyrins
excreted in urine.
• Major morbidity is d/t photosensitivity & skin
fragility & blistering, hampering daily activities.
• Iron is known to inhibit UROD.
• Removal of iron by repeated phlebotomy is standard
treatment, usually leading to remission.

24. SIDEROBLASTIC
ANAEMIA

25. • Group of refractory anaemias
characterized by:
• Variable numbers of hypochromic cells
in peripheral blood.
• Ring sideroblasts comprising 15% or
more of marrow ertyhroblasts.

26. • Siderocyte • Mature red cell containing 1 or more
siderotic granules.
• Normal • Nucleated red cell containing 1 or
sideroblast more siderotic granules:
› Few & difficult to see.
› randomly distributed in cytoplasm.
› reduced proportion of sideroblasts in
iron deficiency & anaemia of chronic
disorders

27. Abnormal sideroblasts
Cytoplasmic iron deposits Mitochondrial iron deposit
• Ferritin aggregates • Non-ferritin iron
• Numerous & larger granules • More than 4
• Easily visible & randomly perinuclear
distributed granules, covering
1/3rd or more of the
• Proportion of sideroblasts
nuclear
usually parallels %
circumference. (Ring
saturation of transferrin.
sideroblasts)
• E.g: haemolytic &
megaloblastic anaemia, iron
overload, thalassaemia
disorders.

28. CLASSIFICATION
ACQUIRED
HEREDITARY
PRIMARY SECONDARY
DRUGS
TOXINS X-LINKED
HAEMATOLOGIC
MYELODYSPLASIA MALIGNANCIES AUTOSOMAL
(RARS)
OTHER BENIGN MITOCHONDRIAL
CONDITIONS

29. HEREDITARY SIDEROBLASTIC
ANAEMIAS:
• Rare disorders
• Manifesting mainly in males
• Onset usually in childhood or
adolescence
• Occasional late presentation

30. X-LINKED
MUTATIONS
ALAS2 ABCB7
MUTATIONS MUTATIONS

31. ALAS2 MUTATIONS:
• More than 25 mutations of the gene for erythroid
specific ALAS2 on X chromosome.
• Most lead to changes in protein structure, causing
instability or loss of function.
• Function may be rescued to a variable degree by
administration of pyridoxal phosphate (B6).
• Response is better if iron overload is removed by
phlebotomy or chelation.

32. • Hypochromic, often microcytic anaemia.
• Bone marrow shows;
› erythroid hyperplasia
› microcytic erythroblasts with vacuolated
cytoplasm
› more than 15% ringed sideroblasts
• Few circulating siderocytes, normoblasts & cells with
punctate basophilia. ( pronounced only if spleen has
been removed)

33. • Erythroid expansion may result in bossing of skull &
enlargement of facial bones.
• Spleen may be enlarged.
• Severe iron overload may occur.
• Female carriers may show partial haematological
expression, depending on the severity of defect in
the enzyme & degree of lyonization of effected X-
chromosome.

34. ABCB7 MUTATIONS
• Rare form of X-linked sideroblastic anaemia
• ABCB7, a transmembrane protein that binds &
hydrolyses ATP, transfers iron-sulphur clusters from
mitochondria to cytosol.
• Iron-sulphur clusters are part of IRP1, which controls
ALAS2, & ferrochelatase enzyme.

35. • Early onset.
• Anaemia is mild to moderately severe.
• Non-progressive cerebellar ataxia. (may be due to
iron damage to mitochondria in neural cells)
• Inc. red cells zinc protoporphyrin level.

37. THTR-1 MUTATIONS
• SLC19A2 gene mutations encoding for THTR-1
• Causes Roger syndrome, an autosomal recessive
disorder.
• Responsible for thiamine responsive megaloblastic
anaemia & DIDMOAD. (diabetes insipidus, diabetes
mellitus, optic atrophy & deafness)
• Ring sideroblasts are typically seen.

38. • Onset is usually in childhood.
• SLC25A38 MUTATIONS:
• Transporter protein which transfers glycine to
mitochondria.
• An essential step in synthesis of ALA.

39. GLUTAREDOXIN-5 (GLRX5) MUTATIONS
• Autosomal recessive disorder.
• This enzyme participates in iron-sulphur cluster
formation.
• Hypochromic microcytic anaemia with ring
sideroblasts.

40. MITOCHONDRIAL
MUTATIONS
MITOCHONDRIAL DNA M
•
Pearson
(marrow- Kearns-Syre
pancreas) syndrome
syndrome

41. PEARSON SYNDROME
• Rare multisystemic cytopathy d/t mitochondrial gene
deletions.
• Marrow failure is the 1st defining feature & all cell
lineages may be effected.
• Macrocytic sideroblastic anaemia typically seen.
• Prominent vacuoles in cells of both myeloid &
erythroid lineages.

43. • Exocrine dysfunction d/t fibrosis & acinar
atrophy, resulting in chronic diarrhoea &
malabsorption.
• Lactic acidemia d/t defect in oxidative
phosphorylation.
• Death often occurs in infancy or early childhood d/t
infection, metabolic crisis &/or multi-organ failure.
• Older survivals develop KSS.

44. KEARSON-SYRE SYNDROME (KSS)
• Rare neuromuscular disorder d/t mitochondrial gene
mutations.
• Onset usually before the age of 20yrs.
• Skeletal muscle weakness.
• Short stature
• Hearing loss

45. • Heart block ( conduction defect)
• Ataxia
• Endocrine dysfunctions
• Impaired cognitive function
• Treatment is generally symptomatic &
supportive.
• Prognosis is usually poor.

46. ACQUIRED
SECONDARY PRIMARY
DRUGS DEFICIENCIES
TOXINS SYSTEMIC RARS
DISEASE

47. REFRACTORY ANAEMIA WITH RING
SIDEROBLASTS (RARS)
• A myelodysplastic syndrome characterized by:
• Anaemia
• Morphologic dysplasia in erythroid lineage
• Ring sideroblasts comprising ≥15% of BM erythroid
precursors.
• No significant dysplasia in non-erythroid lineages.
• Myeloblasts comprise ‹ 5% of nucleated BM cells &
are not present in PB.

48. Epidemiology
• Accounts for 3-11% of MDS cases.
• Occurs primarily in older individuals with a median age
of 60-73yrs.
• Similar frequency in males & females.

49. • Etiology
• A clonal stem cell defect manifesting as
abnormal iron metabolism in erythroid
lineage.
• Acquired defects of mitochondrial DNA
may underlie.
• In contrast to congenital X-linked
defects, red cell protoporphyrin levels
are raised.

50. Morphology
• Anaemia is often normochromic macrocytic.
• PB smear may manifest a dimorphic picture with a
major population of normochromic RBC’s & minor
population of hypochromic cells.
• BM aspirate shows erythroid hyperplasia &
dysplasia, including nuclear lobation & megaloblastoid
features.
• Haemosiderin laden macrophages are often abundant.

51. RING SIDEROBLASTS

52. Bone marrow aspirate
Erythroid precursors vary from mildly dyspoietic to
large, bizarre multinucleated cells.

53. Bone marrow aspirate
Mild megaloblastoid changes but granulocytes have no
dysplastic features.

54. Bone marrow biopsy
Mildly hypercellular with erythroid proliferation.
Megakaryocytes are normal in number & morphology.

55. PB smear
Macrocytic RBC’s (MCV=104).
Mild aniso & poikilocytosis

56. Ring sideroblasts & iron laden
macrophages

57. • Granulocytes & megakaryocytes show no significant
dysplasia.( ‹ 10% dysplastic forms)
• BM biopsy is normocellular to markedly hypercellular.
• 1-2% cases evolve into AML. (less than in other MDS
forms)
• Median survival is 108 months.

58. DRUGS
• Anti-tuberculous
chemotherapy, specially isoniazid &
cycloserine
• (pyridoxine antagonists)
• Chloramphenicol inhibits mitochondrial
protein synthesis.
• Penicillamine (copper chelating agent)
• Hormones (progesterone)
• Copper deficiency ( zinc suppliments)

59. MITOCHONDRIAL TOXINS
• Alcohol
• Lead poisoning

60. • LEAD TOXICITY
• Exposure to high levels of lead typically associated
with severe health effects.
• Minimum Blood Lead Level (BLL) to cause lead
poisoning is 10µg/dL. (WHO guidelines)
• Potential sources: toys, old lead
pipes, cement, paint, lead fuel, canned food etc.

62. Mechanisms of action:
• Binds to sulfhydryl group of proteins causing
denaturation of structural proteins.
• Binds Ca++ activated proteins & effects various
transport systems & enzyme systems.
• Interferes with δ-ALAS & ferrochelatase enzymes.
• Interferes with release of neurotransmitters
specially glutamate by blocking NMDA receptors.

64. • Anaemia is usually normochromic or slightly
hypochromic.
• Haemolysis is often, with a mild rise in
reticulocytes, but jaundice is rare.
• Basophilic stippling on the ordinary (Romanowsky)
stain is characteristic finding. (precipitation of
denatured RNA d/t inhibition of the enzyme
pyrimidine 5’-nucleotidase)
• Siderotic granules, & ocacasionally Cabot rings are
found in circulating red cells.

65. Basophilic Stippling

66. Pappenheimer bodies ( Siderotic granules)

67. Siderotic granules

68. Management:
• Supportive care
• Reduce exposure
• Chelation therapy in extreme cases.

69. Treatment of Sideroblastic Anaemia
• Some patients with X-linked sideroblastic anaemia
respond to pyridoxine.
• Some secondary sideroblastic anaemias may be
completely reversed by pyridoxine therapy.
• Pyridoxine therapy almost always ineffective in
refractory anaemia with ring sideroblasts.
• Folic acid may benefit patients with secondary
anaemias.

70. • In cases of iron overload, anaemia may
improve after phlebotomy or iron
chelation therapy.
• Splenectomy usually does not benefit
anaemia & leads to post-operative high
platelet counts.