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Pediatrics/various sized red blood cells


My 17 month old daughter had blood tests done (as she lost a little bit of weight in stead of gaining) and it shows her red blood cells are various sizes. Her Iron and folic acid levels are normal. Our GP doesn't know why the various size red blood cells? What could be causing this???? We are on the waiting list to see the Pediatrician, but it can take 4 months. Cheers

Hi, Yolandy,

Anisocytosis is the term we use for RBC of varying sizes.  It can occur in a healthy person.  In order to evaluate this fully, one needs to know a number of other parameters in the blood count, including the hemoglobin and RDW.  The RDW is the secret to evaluating this, as this cut and pasted note from the internet indicates:

Anisocytosis is identified by RDW and is classified according to the size of RBC measured by MCV. According to this, it can be divided into

Anisocytosis with microcytosis Iron deficiency, sickle cell anemia
Anisocytosis with macrocytosis Folate or vitamin B12 deficiency, autoimmune hemolytic anemia, cytotoxic chemotherapy, Chronic liver disease, Myelodysplastic syndrome
Increased RDW is seen in iron deficiency anemia, Thalassemia Major (Cooley's anemia), Thalassemia Intermedia and myelodysplastic syndromes

Anisocytosis with normal RBC size Early iron, vit B12 or folate deficiency, dimorphic anemia, Sickle cell disease, chronic liver disease, Myelodysplastic syndrome[2].

As you can see, this is complicated stuff.  If she is healthy and not anemic, then a multi-phased workup is not always needed.  Your doctor has all the info, however, to make some of these broad determinations.  

Good luck, Dr. Olson  


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David Olson, MD


I would be happy to attempt to answer any questions about general pediatric topics, either medical issues or behavioral issues. This would include all the various questions one receives in a busy pediatric practice. I`m a board certified pediatrician in northern Michigan and have been in practice for over 15 years. I enjoy the teaching role I have in our practice and would enjoy the opportunity to help others with their pediatric problems.

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