Saturday, February 9, 2008

Bone Marrow Cellularity

I have loads of medical textbooks on my shelves. Some people buy clothes, I buy books! I have a wonderful book titled: Illustrated Pathology of the Bone Marrow This is what it has to say about the cellularity of the bone marrow:

“It is often easiest to evaluate a bone marrow specimen by comparing it to what would be expected in the normal bone marrow. The initial evaluation on low magnification includes the assessment of sample adequacy and marrow cellularity. The latter is usually based on the biopsy. Estimates of cellularity on aspirate material have been described but may be unreliable in variably cellular marrows. The normal cellularity varies with age and evaluation of cellularity must always be made in the context of the patient’s age. The marrow is approximately 100% cellular during the first three months of life, 80% cellular in children through the age 10 years; it then slowly declines in cellularity until age 30 years, when it remains about 50%cellular. The usually accepted range of cellularity in normal adults is 40-70%. The marrow cellularity declines again in elderly patients to about 30% at 70 years. Because of the variation in cellularity by age, the report should clearly indicate whether the stated cellularity in a given specimen is normocellular, hypocellular or hypercellular.”

I also found this information on a website.

Age related changes in bone marrow

Cellularity averages 79% at ages 0-9 years vs. 50% at ages 30-69 vs. 29% at ages 70-79. With aging, hematopoietic tissue is replaced by fat. Deeper medullary areas are typically more cellular than subcortical areas.

B cell production declines with age (Curr Opin Immunol 2005;17:463), although the relative abundance of pro-B, pre-B, immature, naive, and mature B cells usually does not change appreciably between ages 24 and 88 years; occasional patients have exceptionally low numbers of lymphocyte precursors (Blood 2003;101:576)

Hypocellularity in elderly marrow may be due to increased apoptosis (Mech Ageing Dev 2000;117:57)