Background and Aim: Isolated polycystic liver disease (PCLD) is characterized by the presence of multiple cysts in the liver in the absence of polycystic kidneys. The clinical profile of PCLD is poorly defined and we set up a study for the clinical characteristics of PCLD., Methods: We collected clinical data on 188 PCLD patients (defined as >10 liver cysts) from five tertiary referral centres, and 137 patients were selected for the purpose of this study. We performed molecular analysis of the PCLD associated genes PRKCSH and SEC63 in 91 patients., Results: A total of 118 (86%) patients were female. The majority of patients (88%) had >20 cysts. The median age at diagnosis was 47 years (range 23-84). 37 (41%) patients carried a mutation. Clinical symptoms at presentation were present in 111 (84%) patients. γ-glutamyl transferase was elevated to 1.4 times upper limit of normal (interquartile range 1.0-2.7). The presence of a mutation and female gender predicted a more severe course: female patients were 9 years younger at the time of diagnosis (47 years; range 23-84) and 91% had symptoms (P<0.01); likewise, mutation carriers were younger at presentation (39 years; range 35-48) and 95% of this cohort had symptoms (P<0.01). During follow-up [median 8.2 years (range 0-35)], 10% of untreated and 51% of treated patients developed complications. Mortality in this cohort was 8%, but only 2% died of PCLD-related causes. 58% of patients were treated a median of 2 years (range 0-25) after diagnosis., Conclusion: Symptomatic PCLD patients are mainly females. Females and mutation carriers were younger at diagnosis and had a more severe course of disease., (© 2010 John Wiley & Sons A/S.)