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RBC Inclusions Decoded: Diagnostic Pearls from William Aird
Sep 23, 2025, 19:03

RBC Inclusions Decoded: Diagnostic Pearls from William Aird

 

William Aird, Professor of Medicine at Harvard Medical School, posted on X:

”1/7

RBC INCLUSIONS

Red blood cell (RBC) inclusions: small structures with big diagnostic value. Each one points to a different process, from marrow stress to iron overload to infection.  Here’s a tour, one inclusion at a time.

 

2/7

Nucleated RBCs: immature erythroid precursors that still carry their nucleus.

  • Normally confined to the marrow (except neonates).
  • In circulation, signal marrow under stress (hemolysis, hypoxia, marrow infiltration)

Think of them as a sign of the BM “pushing hard.”

 

3/7

Howell–Jolly bodies: small, round basophilic nuclear remnants (DNA) DNA found within circulating RBCs.

  • Appear when the spleen is absent or not functioning (asplenia, hyposplenism).
  • If you see them, ask about the spleen.

See here.

 

4/7

Basophilic stippling: numerous fine or coarse punctate, blue-purple granules (aggregates of ribosomal RNA).

  • Causes include thalassemia, lead poisoning, sideroblastic anemia.
  • Coarse stippling is especially associated with lead.

 

5/7

 Pappenheimer bodies: iron-containing granules (siderotic granules) in RBCs.

  • Stain positive with Prussian blue
  • Seen in sideroblastic anemia, iron overload, post-splenectomy.

See here.

 

6/7

 Intraerythrocytic parasites: malaria, babesiosis.

  • Morphology varies (rings, trophozoites, schizonts, gametocytes).
  • Always correlate with travel/exposure history; finding parasites in RBCs is a diagnostic emergency.

 

7/7

Red cell inclusions provide direct windows into pathophysiology: nuclear remnants, iron deposits, ribosomal aggregates, or pathogens. Recognizing them is a high-  yield skill at the microscope.”

RBC

 

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