Nonalcoholic fatty liver disease (NAFLD) is a spectrum of liver diseases with histologic features of alcohol induced liver disease that occurs in individuals who do not consume significant quantities of alcohol. The spectrums of the liver diseases include hepatic steatosis (fatty liver); nonalcoholic steatohepatitis (NASH) with histologic evidence of hepatitis, hepatocellular injury, necrosis and, fibrosis; and cirrhosis with eventual portal hypertension and other complications. NAFLD is believed to be one of the most common causes of abnormal liver chemistry tests in American adults. It is thought to be the major cause of cryptogenic cirrhosis. Clinically, NAFLD should be a diagnosis of exclusion. It should be suspected as a cause of chronic liver disease in patients who deny alcohol consumption and have negative serologic tests for active viral, congenital, and acquired causes of liver disease. THE MAJOR FEATURE IN NASH IS FAT IN THE LIVER, ALONG WITH INFLAMMATION AND DAMAGE. MOST PEOPLE WITH NASH FEEL WELL AND ARE NOT AWARE THAT THEY HAVE A LIVER PROBLEM. NEVERTHELESS, NASH CAN BE SEVERE AND CAN LEAD TO CIRRHOSIS, IN WHICH THE LIVER IS PERMANENTLY DAMAGED AND SCARRED AND NO LONGER ABLE TO WORK PROPERLY. IT RESEMBLES ALCOHOLIC LIVER DISEASE, BUT OCCURS OCCUR WITH THE USE OF ALCOHOL (ALCOHOL-RELATED FATTY LIVER) OR IN THE ABSENCE OF ALCOHOL (NONALCOHOLIC FATTY LIVER DISEASE). DISEASE ETIOLOGY: FAT ACCUMULATES IN THE LIVER USUALLY IN CONNECTION WITH HEAVY USE OF ALCOHOL, EXTREME WEIGHT GAIN OR DIABETES MELLITUS. FATTY LIVER CAN ALSO OCCUR WITH POOR DIET AND CERTAIN ILLNESSES, SUCH AS TUBERCULOSIS, INTESTINAL BYPASS SURGERY FOR OBESITY, AND CERTAIN DRUGS SUCH AS CORTICOSTEROIDS. IT MOST OFTEN OCCURS IN PERSONS WHO ARE MIDDLE-AGED AND OVERWEIGHT OR OBESE. MANY PATIENTS WITH NASH HAVE ELEVATED BLOOD LIPIDS, SUCH AS CHOLESTEROL AND TRIGLYCERIDES, AND MANY HAVE DIABETES OR PRE-DIABETES, BUT NOT EVERY OBESE PERSON OR EVERY PATIENT WITH DIABETES HAS NASH. SOME PATIENTS WITH NASH ARE NOT OBESE, DO NOT HAVE DIABETES, AND HAVE NORMAL BLOOD CHOLESTEROL AND LIPIDS. NASH CAN OCCUR WITHOUT ANY APPARENT RISK FACTOR AND CAN EVEN OCCUR IN CHILDREN. THUS, NASH IS NOT SIMPLY OBESITY THAT AFFECTS THE LIVER. SYMPTOMS NASH IS USUALLY A SILENT DISEASE WITH FEW OR NO SYMPTOMS. PATIENTS GENERALLY FEEL WELL IN THE EARLY STAGES AND ONLY BEGIN TO HAVE SYMPTOMS--SUCH AS FATIGUE WEIGHT LOSS WEAKNESS ONCE THE DISEASE IS MORE ADVANCED OR CIRRHOSIS DEVELOPS. THE PROGRESSION OF NASH CAN TAKE YEARS, EVEN DECADES. THE PROCESS CAN STOP AND, IN SOME CASES, REVERSE ON ITS OWN WITHOUT SPECIFIC THERAPY. OR NASH CAN SLOWLY WORSEN, CAUSING SCARRING OR "FIBROSIS" TO APPEAR AND ACCUMULATE IN THE LIVER. AS FIBROSIS WORSENS, CIRRHOSIS DEVELOPS; THE LIVER BECOMES SERIOUSLY SCARRED, HARDENED, AND UNABLE TO FUNCTION NORMALLY. NOT EVERY PERSON WITH NASH DEVELOPS CIRRHOSIS, BUT ONCE SERIOUS SCARRING OR CIRRHOSIS IS PRESENT, FEW TREATMENTS CAN HALT THE PROGRESSION. A PERSON WITH CIRRHOSIS EXPERIENCES FLUID RETENTION, MUSCLE WASTING, BLEEDING FROM THE INTESTINES, AND LIVER FAILURE.