INTRODUCTION: Alpha-1-antitrypsin deficiency (AATD) is a rare disease that is significantly underdiagnosed. In the United Stated, only 10% of the 100,000 individuals with possible AATD have been identified. Through this case, we would like to highlight the importance of ordering the appropriate diagnostic test for early diagnosis of the disease. CASE DESCRIPTION/METHODS: A 50-year-old female with a past medical history of obesity was referred to our hospital for further management of decompensated liver cirrhosis. Her liver disease was complicated by large volume ascites requiring large-volume paracentesis and multiple hospitalizations for hepatic encephalopathy. Her end-stage liver disease was attributed to non-alcoholic fatty liver disease for one year before presentation as liver biopsy was considered inconclusive. On examination, tense ascites was noted. Lab findings showed AST of 45 U/L, ALT of 23 U/L, ALP of 116 U/L, total bilirubin of 2.3 mg/dL, direct bilirubin of 0.9 mg/dL, INR of 1.69 and PT of 15.8 seconds and A1AT levels significantly low at 24 mg/dL with ZZ genotype. A second review of the prior liver biopsy was sought which showed micronodular cirrhosis with PAS-positive globules in hepatocytes consistent with AATD. Her alpha-1-antitrypsin (A1AT) levels were higher in the past and a phenotype test was not obtained by her previous provider. A1AT can be falsely elevated at times of inflammation leading to a delay in diagnosis. DISCUSSION: AATD is an autosomal recessive disease that causes liver, lung, and skin disease in both adults and children. Individuals with this genetic disorder produce large quantities of A1AT mutant Z protein that gets misfolded and retained in the liver instead of being secreted. These retained intracellular polymers trigger a cascade of intracellular injury. AATD is underdiagnosed due to its non-specific presentation with an average delay in diagnosis of 5.6 years. All patients with liver disease of unclear etiology should be tested. Serum levels of A1AT can be falsely elevated in the setting of inflammation as it is also an acute-phase reactant. Hence, phenotyping by isoelectric focusing is the gold standard of diagnosis. Currently, liver transplantation is the only available treatment for end-stage liver disease and patients have excellent prognosis post-transplantation. With timely diagnosis, the progression of lung disease can also be prevented with intravenous augmentation therapy of pooled human A1AT protein.