A 35 year old female evaluated for anemia has a dry marrow tap and a peripheral smear showing tear drop cells. What is the most likely diagnosis?
**Core Concept**
Myelofibrosis is a disorder characterized by the progressive fibrosis and scarring of the bone marrow, leading to ineffective hematopoiesis and extramedullary hematopoiesis. Tear drop cells on a peripheral smear are a hallmark of marrow fibrosis.
**Why the Correct Answer is Right**
The presence of tear drop cells on a peripheral smear, along with a dry marrow tap, is highly suggestive of myelofibrosis. This is because the fibrosis in the bone marrow leads to the extrusion of red blood cells into the peripheral circulation, which can cause these cells to become misshapen and take on a characteristic "tear drop" appearance. The dry marrow tap is also indicative of marrow fibrosis, as the fibrotic tissue makes it difficult to aspirate marrow cells.
**Why Each Wrong Option is Incorrect**
**Option A:** Sickle cell anemia can cause a variety of abnormalities on a peripheral smear, including target cells and sickled red blood cells, but it is not typically associated with tear drop cells or a dry marrow tap.
**Option B:** Leukemia can cause anemia and abnormalities on a peripheral smear, but it is not typically associated with tear drop cells or a dry marrow tap.
**Option C:** Thalassemia can cause a variety of abnormalities on a peripheral smear, including target cells and microcytosis, but it is not typically associated with tear drop cells or a dry marrow tap.
**Clinical Pearl / High-Yield Fact**
The presence of tear drop cells on a peripheral smear, along with a dry marrow tap, is a classic finding in myelofibrosis. This is often referred to as the "dry tap" sign, and it is a key diagnostic clue for this disorder.
**Correct Answer:** C. Myelofibrosis.