Objective To find the genetic etiology of premature ovarian insufficiency (POI) in a patient with primary amenorrhea and hypergonadotropic hypogonadism. Design Case report. Setting University hospital. Patient(s) A Belgian woman aged 32 years with POI at the age of 17, her parents, and her sister whose POI was diagnosed at age 29. Intervention(s) Analysis of a panel of 31 genes implicated in POI (POIGP) using next-generation sequencing (NGS), Sanger sequencing, and in vitro functional study. Main Outcome Measure(s) Gene variants, family mutational segregation, and in vitro functional impact of the mutant proteins. Result(s) The analysis of the gene panel using NGS identified the presence of two novel follicle-stimulating hormone receptor (FSHR) missense mutations at a compound heterozygous state in the affected patient: c.646 G>A, p.Gly216Arg, and c.1313C>T, p.Thr438Ile. Sanger sequencing showed the presence of each mutation at heterozygous state in the patient’s parents and at heterozygous compound state in the affected sister. Both substituted amino acids (Gly216 and Thr438) were conserved in FSHR of several vertebrate species as well as in other glycoproteins receptors (TSHR and LHCGHR), suggesting a potentially important role in glycoprotein receptor function. An in vitro functional study showed similar results for both variants with more than 90% reduction of their cell surface expression and a 55% reduction of their FSH-induced cyclic adenosine 3′:5′ monophosphate (cAMP) production compared with the wild-type FSHR. Conclusion(s) The analysis of a gene panel of 31 genes implicated in POI allowed us to identify two novel partially inactivating mutations of FSHR that are likely responsible for the POI phenotype of the proband and of her affected sister.