Hepatic steatosis in non-alcoholic fatty liver disease (NAFLD) is histologically graded using the NAFLD Activity Score (NAS). Which histological feature, when present, distinguishes NASH from simple steatosis?

• A Macrovesicular steatosis
• B Ballooning degeneration of hepatocytes with lobular inflammation ✓
• C Periportal fibrosis (Stage 1b)
• D Glycogenated nuclei in periportal hepatocytes

Explanation

The NAS (NAFLD Activity Score) combines steatosis (0–3), lobular inflammation (0–3), and hepatocyte ballooning (0–2). Hepatocyte ballooning — swelling with pale, reticular cytoplasm and loss of cytoskeletal integrity (loss of cytokeratin 18) — is the hallmark distinguishing NASH from simple steatosis. Lobular inflammation is also required for the NASH diagnosis. Simple steatosis shows only macrovesicular fat without ballooning or significant inflammation. Periportal fibrosis is a stage of fibrosis, and glycogenated nuclei occur in diabetes/glycogen storage but are not the NASH-defining feature.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

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Written and medically reviewed by the StethoPrep medical team.