Novel estrogen receptor-α gene inactivating missense variant in a woman: Therapeutic challenge and long-term follow-up data.

Background: Rare mutations of the ESR1 gene, encoding the estrogen receptor alpha (ERα), have been shown to cause estrogen resistance in humans. Phenotypic features include impaired maturation of epiphyseal cartilage, osteoporosis, and infertility. Clinical phenotype is not well described and the available data reflect inconsistency. To date, there are no effective therapeutic options.

Method: This retrospective study provides a detailed description of bone and metabolic phenotype and 8-year follow-up data of a female with a novel p.Met543Thr missense variant in the homozygous state, localized in the ligand-binding domain.

Results: The patient, first seen at the age of 21.3 years, presented with a tall stature (+2.2 SD), a delayed bone age (13 years). She had no breast development, normal axillary and pubic pilosity and bilateral axillary acanthosis nigricans. The metabolic phenotype included insulin resistance, decreased insulin sensitivity and increased leptinemia. The patient presented a continuous linear growth (height + 3SD at the age of 28.6 years). She had a severe osteoporosis of the lumbar spine (Z-score -3.9) and osteopenia of the femoral neck (Z-score -1.8). Osteoporosis worsened (Z-score -5.6 at the lumbar spine; Z-score -4.4 at the femoral neck) despite successive treatments with ethinyl-estradiol and tamoxifen (selective estrogen modulator). Markers of bone turnover were increased and unresponsive to treatment. Treatment with ethinyl-estradiol improved insulin sensitivity, lowered leptinemia, increased some estrogen-regulated liver proteins and the E2/T ratio.

Conclusion: This report brings new insights to the estrogen resistance syndrome and improves our understanding of the skeletal and tissue specific roles of ERα in humans.