**Question:** Basophils are decreased in

A. Leukopenia
B. Hyperthyroidism
C. Acute leukemia
D. Chronic myeloid leukemia

**Core Concept:** Basophils are a type of white blood cell (WBC) that play a role in the immune system, particularly in allergic reactions and defense against parasites. They are part of the granulocyte family, which also includes neutrophils and eosinophils.

**Why the Correct Answer is Right:** Basophils are decreased in Leukopenia (a condition characterized by a decrease in total WBC count). This can be due to various reasons such as bone marrow suppression, inadequate production, or increased destruction. In some cases, leukopenia can be a manifestation of underlying diseases or conditions, like infections, malignancies (e.g., lymphoma), or medications.

**Why Each Wrong Option is Incorrect:**

A. Hyperthyroidism: Basophils are typically not affected by hyperthyroidism, a condition characterized by overproduction of thyroid hormones. Hyperthyroidism may lead to leukocytosis (increased total WBC count), as seen in neutrophilia and lymphocytosis.

B. Hyperthyroidism: Similar to the previous explanation, basophils are not typically affected in hyperthyroidism, which leads to an overall increase in WBC count.

C. Acute leukemia: Acute leukemia is a condition characterized by rapid proliferation and maturation arrest of immature blood cells, including basophils. In acute leukemia, basophil count is usually decreased due to the increased destruction of immature basophils.

D. Chronic myeloid leukemia: Chronic myeloid leukemia is a type of leukemia characterized by increased production of myeloid cells, including basophils. While basophil count may be decreased in the early stages of chronic myeloid leukemia, it is typically increased in chronic granulocytic leukemia.

**Clinical Pearl:** Leukopenia (decreased WBC count) can be a sign of underlying disease or medication-induced toxicity. A thorough clinical history, physical examination, and investigations are required to determine the cause of leukopenia.

**Correct Answer:** Leukopenia (A)

**Explanation:** Leukopenia can be seen in various conditions affecting the bone marrow or overall health status, making it important to assess the patient's clinical history and examine for signs of infection, inflammation, or malignancy. Additionally, certain medications may cause leukopenia as a side effect, such as corticosteroids and chemotherapeutic agents. A thorough evaluation and understanding of the patient's medical history are crucial in determining the cause of decreased WBC count.