**Question:** In a middle-aged man the radiograph shows 'cotton-wool' appearance and blood investigation reveal an elevated alkaline phosphatase levels. The tentative diagnosis is:

A. Wilson's disease
B. Primary biliary cirrhosis
C. Primary liver cancer
D. Alkaline phosphatase hyperplasia

**Core Concept:**
The 'cotton-wool' appearance on radiography is a term used to describe the radiographic finding of a bright, round, and well-circumscribed area of increased density in the liver. This is usually seen in conditions that cause intrahepatic cholestasis, which leads to bile accumulation and the characteristic radiographic appearance. Alkaline phosphatase (ALP) is an enzyme that is elevated in conditions affecting the liver and bile ducts.

**Why the Correct Answer is Right:**
The correct answer is **B. Primary biliary cirrhosis (PBC)** because this condition is characterized by the destruction of bile ducts leading to cholestasis and subsequent elevated ALP levels. The radiographic appearance of a 'cotton-wool' spot in the liver is consistent with this diagnosis. Other options do not have this specific radiographic finding or have different aetiologies associated with elevated ALP levels.

**Why Each Wrong Option is Incorrect:**
A. Wilson's disease (WD) is a different liver disorder caused by copper accumulation, which results in a different radiographic appearance and does not typically present with a 'cotton-wool' appearance.

C. Primary liver cancer (hepatocellular carcinoma) usually presents with other clinical symptoms, signs, and radiographic findings. It is not specifically associated with the 'cotton-wool' appearance and elevated ALP levels.

D. Alkaline phosphatase hyperplasia is not a correct medical term, and none of the other options are associated with this condition.

**Clinical Pearl:**
Primary biliary cirrhosis (PBC) is a rare autoimmune liver disease characterized by the destruction of bile ducts. The 'cotton-wool' appearance on radiography and elevated ALP levels are key features in diagnosing PBC, which is essential to differentiate it from other liver diseases.