Q. Does medullary expansion mainly happen in alpha thalassemia patients because they cannot make any useful hemoglobin due the the absence of the alpha chain? Or does it occur in both alpha and beta thalassemias?

A. Medullary expansion can happen in severe thalassemia of either alpha or beta type. Patients have a severe anemia due to the lack of either alpha or beta chains, and the body tries to compensate by making marrow wherever it can.

Q. DDAVP is a nasal spray correct? I read that DDAVP helps increase the production of VWF and VIII, but that doesn’t really make sense since the factor VIII is already there, there is no need to make more of it? right? The issue isn’t lack of factor VIII its lack of vW which carries the factor VIII.

A. Yes, DDAVP is a nasal spray. It happens to increase the level of both von Willebrand factor and factor VIII, by mechanisms which are not completely understood. So it can be useful in both von Willebrand disease and hemophilia A. You’re right that in von Willebrand disease the decreased level of factor VIII (if present) is due to the decreased level of vWF, which is the carrier for factor VIII. So really, the main usefulness of DDAVP in vWF lies in its ability to increase vWF. It doesn’t hurt to increase the level of factor VIII, while you’re at it, but really, you could just increase vWF and the factor VIII level would come up on its own.

Q. What is important to know about vaso-occlusive disease (in relation to sickle cell anemia) other than it causes massive enlargement to the spleen which eventually becomes small and fibrotic in adulthood?

A. You’re right that vaso-occlusive disease causes autosplenectomy. It also causes lots of other nasty things, like pulmonary embolism, stroke, heart attack, skin ulceration – basically anything you can imagine related to occlusion of capillary beds or small vessels. It’s the cause of much of the morbidity in sickle cell disease; it’s often what brings a patient into the hospital.

Q. I’m looking at the coagulation cascade and it looks like factors VIIIa and Va are designated differently than the other factors. Could you please explain this?

A. Sure. Factors V and VIII are “cofactors” – they help out the cascade by making it go much faster. They are like little amplifiers; once they get activated it’s like an explosion takes place, the cascade goes so fast.