Fil: Espeche, Lucía Daniela. ANLIS Dr.C.G.Malbrán. Centro Nacional de Genética Médica; Argentina.Fil: Chiauzzi, Violeta. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental; Argentina.Fil: Ferder, Ianina. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental; Argentina.Fil: Arrar, Mehrnoosh. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Química-Física de los Materiales, Medio Ambiente y Energía; Argentina.Fil: Solari, Andrea Paula. ANLIS Dr.C.G.Malbrán. Centro Nacional de Genética Médica; Argentina.Fil: Bruque, Carlos David. ANLIS Dr.C.G.Malbrán. Centro Nacional de Genética Médica; Argentina.Fil: Delea, Marisol. ANLIS Dr.C.G.Malbrán. Centro Nacional de Genética Médica; Argentina.Fil: Belli, Susana. Hospital de Agudos Carlos G. Durand. División de Endocrinología; Argentina.Fil: Fernández, Cecilia Soledad. ANLIS Dr.C.G.Malbrán. Centro Nacional de Genética Médica; Argentina.Fil: Buzzalino, Noemí Delia. ANLIS Dr.C.G.Malbrán. Centro Nacional de Genética Médica; Argentina.Fil: Charreau, Eduardo Hernán. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Biología y Medicina Experimental; Argentina.Fil: Dain, Liliana Beatriz. ANLIS Dr.C.G.Malbrán. Centro Nacional de Genética Médica; Argentina.The premutation state of FMR1 (Fragile X Mental Retardation 1) has been associated with primary ovarian insufficiency (POI), and is the most common known genetic cause for 46,XX patients. Nevertheless, very few studies have analyzed its frequency in Latin American populations. Additionally, a relationship between alleles carrying a cryptic microdeletion in the 5'UTR of FMR2 and the onset of POI has only been studied in one population. Our aim was to analyze the incidence of FMR1 premutations and putative microdeletions in exon 1 of FMR2 in a cohort of Argentinean women with POI. We studied 133 patients and 84 controls. Fluorescent PCR was performed, and the FMR2 exon 1 was further sequenced in samples presenting less than 11 repeats. We found the frequency of FMR1 premutations to be 6.7% and 2.9% for familial and sporadic patients, respectively. Among controls, 1/84 women presented a premutation. In addition, although we did not find microdeletions in FMR2, we observed a change (T >C) adjacent to the repeats in two sisters with POI. Given the repetitive nature of the sequence involved, we could not ascertain whether this represents a single nucleotide polymorphism (SNP) or a deletion. Therefore, a relationship between FMR2 and POI could not be established for our population.