**Core Concept**
The patient is likely suffering from a condition characterized by splenomegaly, leucopenia, and an acute abdominal event, leading to death. This clinical presentation is suggestive of a hematological disorder with involvement of the spleen.

**Why the Correct Answer is Right**
The patient's symptoms are consistent with a diagnosis of acute splenic rupture, which is a known complication of infectious mononucleosis (caused by Epstein-Barr virus). The infection leads to splenomegaly and leucopenia. The acute abdominal event is likely due to splenic rupture, which can be fatal. The spleen is a key organ in filtering the blood and storing lymphocytes, and its rupture can cause severe bleeding and shock.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is not relevant to the clinical presentation described. While splenic rupture can occur in other conditions, the specific combination of symptoms and signs in this patient points to a different diagnosis.
* **Option B:** This option is incorrect because it does not align with the clinical presentation of splenomegaly and leucopenia. The spleen is not typically affected in this condition.
* **Option C:** This option is not a likely finding on autopsy in this context. While the spleen may be affected, the primary issue is the acute abdominal event, which is likely due to splenic rupture.

**Clinical Pearl / High-Yield Fact**
Infectious mononucleosis is a common cause of splenomegaly in adolescents and young adults. The patient's symptoms and signs, including prolonged fever, abdominal discomfort, and splenomegaly, are classic for this condition. A high index of suspicion is necessary to diagnose this condition, as it can be fatal if not recognized and managed promptly.

**Correct Answer: D.**