THU201 Atypical Presentation Of Kallmann Syndrome With A Rare Genetic Mutation

Disclosure: E.L. Montgomery: None. B. Thrasher: None. S. Watson: None. Kallmann Syndrome presents as idiopathic hypogonadotropic hypogonadism with additional findings of hyposmia or anosmia and midline facial defects, including cleft lip/palate. We present a case of Kallmann Syndrome due to a rare genetic mutation with absent Mullerian structures. A 15 year, 6 month old female with history of cleft lip and palate and short stature was referred for primary amenorrhea. Clinical history was notable for limited sense of smell and no signs of puberty, including thelarche or adrenarche. Family History unknown (adopted). Significant physical exam findings include tanner 1 breast, no pubic or axillary hair, normal external female genitalia without clitoromegaly, unestrogenized vaginal introitus. Height 147cm (0.88%ile for age). Lab evaluation consisted of: LH 0.66 mIU/ml (2.4-12.6 mIU/ml), FSH 1.63 mIU/ml (3.5-12.5 mIU/ml), prolactin 11.30 ng/ml (4.79-23.30 ng/ml), BhCG negative, testosterone 8 ng/dl (2-17 ng/dl), free testosterone 1.1 pg/ml (<2.2 pg/ml), estradiol 3.0 pg/ml (9.0-249.0 pg/ml), AMH 2.46 ng/ml (1.05-12.86 ng/ml), thyroid function testing and growth factors normal. Imaging included pelvic ultrasound that showed no uterus or gonads. An MRI was obtained that confirmed these findings and also a blind-ending vaginal canal. While the presentation is suggestive of Kallmann Syndrome, the lack of Mullerian structures on imaging has not previously been described. Further evaluation included karyotype (46, XX) and hypogonadotropic hypogonadism genetic panel that identified a mutation in the FGFR1 gene with c.2172C>G (p.Asn724Lys), heterozygous, variant of uncertain significance. Estrogen replacement therapy was initiated with subsequent expected pubertal progression. Repeat imaging after seven months of treatment demonstrated presence of normal developing uterus and bilateral ovaries. Clinical Lesson/Conclusion: 1.Rare mutation with now 3 reports suggesting it is a true pathologic variant2.Unique presentation with hypoplastic Mullerian structures not detected on imaging.This patient’s particular variant has previously been described in in 2 individuals (mother/son) with features of Kallmann Syndrome (PMID: 16606836) with normal and partial puberty respectively, increasing the suspicion that this variant is pathogenic. Newly described FGFR1 variant associated with Kallmann Syndrome / hypogonadotropic hypogonadism. Kallmann Syndrome is not associated with lack of Mullerian structures, however this patient presented with features of Kallmann Syndrome and imaging that did not demonstrate presence of Mullerian structures. Since initiating estrogen therapy, she has had appropriate development of uterus and ovaries. This case demonstrates that prior to estrogen therapy, patients with Kallmann Syndrome may have underdeveloped Mullerian structures that not recognized on imaging prior to estrogen replacement therapy. Presentation: Thursday, June 15, 2023