**Question:** Koenen's tumour is seen in

A. Multiple Myeloma
B. Lymphoma
C. Chronic Lymphocytic Leukemia (CLL)
D. Chronic Myeloid Leukemia (CML)

**Core Concept:** Koenen's tumour, also known as POEMS syndrome, is a rare paraneoplastic disorder characterized by multiple end organ damage and multiple myeloma. It is classified as a monoclonal gammopathy of undetermined significance (MGUS) or multiple myeloma.

**Why the Correct Answer is Right:** Koenen's tumour is primarily associated with multiple myeloma. The primary feature of this disorder is the presence of a monoclonal plasma cell proliferation, which secretes a monoclonal protein (IgM, IgG, or IgA) into the blood and urine, leading to end organ damage and multiple end-organ dysfunction.

**Why Each Wrong Option is Incorrect:**

A. Multiple Myeloma (Koenen's tumour) is not seen in Multiple Myeloma itself; rather, it is a complication of the disease.
B. Lymphoma is unrelated to Koenen's tumour, as it is a lymphoproliferative disorder, while Koenen's tumour is associated with plasma cell dyscrasias.
C. Chronic Lymphocytic Leukemia is a lymphoproliferative disorder, distinct from Koenen's tumour, which is associated with plasma cell dyscrasias.
D. Chronic Myeloid Leukemia is a myeloproliferative disorder, unrelated to Koenen's tumour.

**Clinical Pearl:** Understanding the relationship between Koenen's tumour and its association with plasma cell dyscrasias is essential for recognizing this rare paraneoplastic syndrome in patients with monoclonal gammopathies. A thorough clinical evaluation and laboratory investigations are necessary to diagnose this condition accurately and initiate appropriate management strategies.