A 32-year-old man of non-consanguineous Chinese parentage, with high-grade fever, rash, joint pain, nausea, and vomiting, was diagnosed as adult-onset still's disease at his initial admission. Although prednisone had been taken, the patient presented with recurrent high-grade fever, rash, splenomegaly, hypertriglyceridemia, cryptogenic hepatitis, apparently elevated levels of serum ferritin(>20,000 μg/L), which met the proposed HLH diagnostic criteria, 2009. Sequence analysis of genomic DNA from the patient's peripheral blood demonstrated heterozygous for UNC13D mutation: c. 1232 G>A, and AP3B1 mutation: c. 1075 A>G, which were predicted to be pathogenic. Unfortunately, at the time, molecular confirmation results for HLH were obtained, and this patient had died from progressive HLH disease with multiple organ dysfunction syndrome caused by shock. FHL should be considered in the differential diagnosis of adults who present with adult-onset still's disease-like symptoms.