Cabot Rings
Created 26 February 2018, last update 6 January 2021 (revised to new
format)
Overview
Look what I saw down the microscope two
years ago. Cabot rings are thin, red-violet staining, threadlike strands in the
shape of a loop or figure of eight that are found on rare occasions in red
blood cells They are thought to be the
microtubules which are all that remains of mitotic spindles. Their presence
indicates an abnormality in erythropoiesis. There’s an
entry on the things in Wikipedia (so it must be true!)
They are incredibly rare; for all that I’ve seen them in text books, I can’t remember seeing any in real life before.
The patient presenting this had a congenital dyserthyopoetic
anaemia. There’s a more scholarly article on the things here.
But look at the case in which this ring presented (It’s
not really him from Star Trek!)
. 
It struck me as rather interesting
that such an unusual morphological finding would occur in such a mundane blood
count; other than a mild anaemia there is not a lot wrong with the blood count.
I can only assume that a CDA on presentation would have something in the blood
count prompting preparation of a blood film.
And it is amazing that although a
hundred years have passed, we still do not know the clinical significance of
Cabot ring
Some More Expert Opinion…
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4712430/
https://imagebank.hematology.org/image/60925/cabot-ring
https://imagebank.hematology.org/image/62463/cabot-ring-in-hemolytic-anemia