Carriers of isodicentric Y (idicY) mosaicism exhibit a wide range of clinical features, including short stature, gonadal abnormalities, and external genital anomalies. However, the phenotypic spectrum for individuals carrying an idicY and a 46, XX cell line is less clearly defined. A more complete description of the phenotype related to idicY is thus essential to guide management related to pubertal development, fertility, and gonadoblastoma risk in mosaic carriers. Findings from the evaluation of twin females with an abnormal karyotype, 48, XX, +idic(Yq) x2/47, XX, +idic(Yq)/46, XX, are presented to highlight the importance of interdisciplinary care in the management of multifaceted disorders of sex development.