**Question:** In tumour lysis syndrome all of the following are seen except -

A. Hyperuricaemia
B. Hyperphosphataemia
C. Hyperkalemia
D. Hypocalcaemia

**Core Concept:**

Tumour lysis syndrome (TLS) is a potentially life-threatening complication that can occur when rapidly growing tumours are destroyed, leading to the release of cellular contents into the bloodstream. This process results in the disturbance of electrolyte balance, acid-base status, and renal function. The key components of TLS involve the release of uric acid, phosphorus, potassium, and calcium due to rapid tumour cell death.

**Why the Correct Answer is Right:**

In tumour lysis syndrome, the main concern is the rapid release of catabolites from the dying tumour cells which leads to deranged electrolyte levels. Hypocalcaemia (decreased calcium levels) is not a typical feature of TLS. While the other options are observed due to the release of uric acid, phosphorus, potassium, and calcium, hypocalcaemia is not a common finding.

**Why Each Wrong Option is Incorrect:**

A. Hypouricaemia (decreased uric acid levels) might be seen in TLS, but hyperuricaemia (increased uric acid levels) is more commonly observed due to the rapid release of uric acid from dying tumour cells.

B. Hypophosphataemia (decreased phosphorus levels) might be seen in TLS, but hyperphosphataemia (increased phosphorus levels) is more commonly observed due to the release of phosphorus from the dying tumour cells.

C. Hyperkalemia (increased potassium levels) is a common finding in TLS, as the release of potassium from the dying tumour cells leads to elevated potassium levels.

**Clinical Pearl:**

Tumour lysis syndrome is a clinical entity that highlights the importance of monitoring electrolyte levels in patients with rapidly growing tumours undergoing treatment. Adequate management of TLS involves prompt recognition, aggressive hydration, and pharmacological intervention to prevent complications.

**Correct Answer:** Hypouricaemia (option D) is incorrect because the main focus in TLS is the derangement of uric acid, phosphorus, potassium, and calcium levels. Hypouricaemia is less common compared to the other components.