Histological Severity and Clinical Outcomes of Nonalcoholic Fatty Liver Disease in Nonobese Patients

Although nonalcoholic fatty liver disease (NAFLD) is closely linked to obesity, around 10%-20% of nonobese Americans and Asians still develop NAFLD. Data on this special group are limited. We therefore studied the severity and clinical outcomes of nonobese NAFLD patients. Consecutive NAFLD patients who underwent liver biopsy were prospectively recruited. We used the NASH Clinical Research Network system to score the histology. The Asian body mass index cutoff of 25 kg/m2 was used to define nonobese NAFLD. Among 307 recruited NAFLD patients, 72 (23.5%) were nonobese. Compared to obese patients, nonobese patients had lower NAFLD activity score (3.361.3 vs. 3.861.2; P50.019), mainly contributed by steatosis (1.760.8 vs. 2.060.8; P50.014) and presence of hepatocyte ballooning (60.9% vs. 73.4%; P50.045). Similarly, nonobese patients had lower fibrosis stage (1.361.5 vs. 1.761.4; P50.004), serum cytokeratin-18 fragments (283 vs. 404 U/L; P < 0.001) and liver stiffness measurement by transient elastography (6.3 vs. 8.6 kilopascals; P < 0.001). By multivariate analysis in nonobese patients, only elevated serum triglyceride level was independently associated with higher NAFLD activity score (adjusted odds ratio [OR], 1.644; P50.021), whereas elevated creatinine level was the only factor associated with advanced fibrosis (adjusted OR, 1.044; P50.025). After a median follow-up of 49 months, 6 patients died, 2 developed hepatocellular carcinoma, and 1 had liver failure, all of whom were in the obese group. Conclusion: Nonobese NAFLD patients tend to have less-severe disease and may have a better prognosis than obese patients. Hypertriglyceridemia and higher creatinine are the key factors associated with advanced liver disease in nonobese patients.