80 year old, asymptomatic man present with a total leucocyte count of I lakh, with 80% lymphocytes and 20% PMC’s. What is the most probable diagnosis?
**Core Concept**
The given total leucocyte count and differential count suggest an increase in lymphocytes, which can be due to various causes, including infections, autoimmune diseases, or malignancies. In this context, the presence of 20% polymorphonuclear cells (PMCs) indicates a partial shift to a neutrophilic response, which is often seen in chronic infections.
**Why the Correct Answer is Right**
The patient's age, asymptomatic presentation, and laboratory findings are suggestive of a chronic infection, particularly one caused by a virus or a fungus that affects the elderly population. The partial shift to a neutrophilic response (20% PMCs) indicates a chronic or subacute process. This pattern is often seen in cases of chronic viral infections, such as cytomegalovirus (CMV) or varicella-zoster virus (VZV), or fungal infections like histoplasmosis or coccidioidomycosis.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not account for the partial shift to a neutrophilic response, which is a key feature in this case. A pure lymphocytosis with no neutrophilic response is more typical of lymphoma or other malignancies.
**Option B:** This option is incorrect because it does not consider the patient's age and asymptomatic presentation. A young patient with a high fever and a severe neutrophilic response would be more likely to have a bacterial infection.
**Option C:** This option is incorrect because it is too broad and does not take into account the specific laboratory findings. A chronic infection is a possible diagnosis, but the partial shift to a neutrophilic response and the patient's age are more specific clues.
**Clinical Pearl / High-Yield Fact**
In elderly patients with a chronic infection, always consider the possibility of an opportunistic infection, such as histoplasmosis or coccidioidomycosis, especially if they have a history of immunosuppression or underlying medical conditions.
**Correct Answer:** D. Chronic infection.