Undiagnosed Thrombocytopenia

From an anonymous inquirer:

I have been misdiagnosed for years. I have very large and oval-shaped platelets which my average count is 40,000. I also tell whoever is taking my complete blood count (CBC) to make sure it is a manual count because my platelets are too large for the machine. I have great coagulation time and everything else is right on the money. No bleeding, bruising or anything out of the sort. It runs down from my mother’s side. I was wondering if the size of the needle could possibly damage some of the platelets because they are so large, resulting in a lower number and I was wondering if you have ever heard of this? Nobody in my family with it has ever been diagnosed with cancer, heart disease or anything of the sort. Everyone has died from natural causes. I do not have the antibodies. I have been treated with IVIG while pregnant and steroids with no results no change at all with my platelet number. I mean everything is right on target except this one minor thing and nobody seems to really care except to try and get more money, but no answers. Thank you for your time.

Hello, and thank you for your question. I’ll begin with the usual disclaimers: I’m not a physician, and if I were, physicians scrupulously avoid making online diagnoses because they need access to medical records to get the whole picture. However, your question is too interesting to simply avoid.

The next time you see a physician during a routine visit, you may suggest she look for one of the MYH9-related thrombocytopenia syndromes. MYH9 is the name for a mutation in a chromosome 22 gene that codes for a protein called myosin. The most commonMYH9 syndrome is May-Hegglin anomaly, an asymptomatic inherited (autosomal dominant) thrombocytopenia with giant platelets. The hallmark of May-Hegglin is the presence of Dohle bodies, light-blue areas in the cytoplasm of certain white cells called neutrophils and eosinophils. Our laboratory instruments do not identify Dohle bodies, they are found by skilled laboratory scientists performing blood film examinations, which are often ordered as a part of the CBC.

The CBC with blood film examination is inexpensive, and is probably all you need. If you want to spend some “real” money, you may choose to ask your physician to follow up with platelet aggregometry, electron microscopy, and molecular testing. This effort is largely academic, and probably wastes resources, but may have some minimal value as it distinguishes May-Hegglin from some exceedingly rare MYH9 disorders, Fechtner syndrome, Sebastian syndrome, and Epstein syndrome. These syndromes do not produce Dohle bodies and require extensive testing to diagnose, but are occasionally associated with mild bleeding, renal (kidney) failure, hearing loss, and cataracts.

There are a number of additional asymptomatic hereditary thrombocytopenias with obscure names or no names, and you can “chase your tail” trying to nail down a diagnosis. It is a good idea to let your laboratory scientist know about your thrombocytopenia and large platelets, and to suggest a manual count. It is possible that a small portion of your platelets could rupture, both during the blood collection process and during the slide-making process, and if they are large enough, some profiling instruments could mis-classify them as red blood cells, falsely elevating your red blood cell count.

I’ve sent your question to a platelet expert who may have more to add in the comment section below. I hope to hear from him in a few days. Meanwhile, thank you for your interesting question, and I wish you continued good health. Geo.