Anosmia with hypogonadism: but NOT Kallmann syndrome

A Family With Novel X-Linked Recessive Homozygous Mutation in ANOS1 (c.628_629 del, p.1210fs∗) in Kallmann Syndrome Associated Unilateral Ptosis: Case Report and Literature Review

OBJECTIVE

Kallmann syndrome (KS) may be accompanied by anosmia or hyposmia and midline defects. We present an overweight 16-year-old boy with a lack of puberty, anosmia, congenital right eye ptosis, and normal intellectual function.

METHODS

Testicular ultrasonography was performed. Whole-exome sequencing was performed on peripheral blood specimens. Genetic results were confirmed by Sanger sequencing. Anosmia was evaluated quantitatively using the Korean version of the Sniffin' stick test II.

RESULTS

Our patient presented with a complaint of lack of body hair growth and small penile size with no remarkable medical history. He was the second son of third-degree consanguineous healthy parents. Physical examination revealed pubertal Tanner stage I. Congenital right eye ptosis and obesity were noted. Anosmia was confirmed. The laboratory evaluation revealed a low serum level of testosterone, follicle-stimulating hormone, and luteinizing hormone. An X-linked recessive homozygous mutation, c.628_629 del (p.1210fs∗) in exon 5 of the ANOS1 gene was revealed and was also found in the patient's uncle and great uncle on the mother's side.

CONCLUSION

To date, approximately 28 ANOS1 mutations producing KS phenotypes have been described. However, to the best of our knowledge, this particular X-linked recessive mutation has not been previously reported in KS. Furthermore, ptosis is a rare finding in KS literature. Identification of these cases increases awareness of the phenotypic heterogeneity in novel forms of KS, thereby expediting early definitive treatment, which may prevent the development of further complications.

Insight Into the Ontogeny of GnRH Neurons From Patients Born Without a Nose

CONTEXT

The reproductive axis is controlled by a network of gonadotropin-releasing hormone (GnRH) neurons born in the primitive nose that migrate to the hypothalamus alongside axons of the olfactory system. The observation that congenital anosmia (inability to smell) is often associated with GnRH deficiency in humans led to the prevailing view that GnRH neurons depend on olfactory structures to reach the brain, but this hypothesis has not been confirmed.

OBJECTIVE

The objective of this work is to determine the potential for normal reproductive function in the setting of completely absent internal and external olfactory structures.

METHODS

We conducted comprehensive phenotyping studies in 11 patients with congenital arhinia. These studies were augmented by review of medical records and study questionnaires in another 40 international patients.

RESULTS

All male patients demonstrated clinical and/or biochemical signs of GnRH deficiency, and the 5 men studied in person had no luteinizing hormone (LH) pulses, suggesting absent GnRH activity. The 6 women studied in person also had apulsatile LH profiles, yet 3 had spontaneous breast development and 2 women (studied from afar) had normal breast development and menstrual cycles, suggesting a fully intact reproductive axis. Administration of pulsatile GnRH to 2 GnRH-deficient patients revealed normal pituitary responsiveness but gonadal failure in the male patient.

CONCLUSIONS

Patients with arhinia teach us that the GnRH neuron, a key gatekeeper of the reproductive axis, is associated with but may not depend on olfactory structures for normal migration and function, and more broadly, illustrate the power of extreme human phenotypes in answering fundamental questions about human embryology.