Hyposmia-nasal and ocular hypoplasia-hypogonadotropic hypogonadism syndrome

Hyposmia-nasal and ocular hypoplasia-hypogonadotropic hypogonadism syndrome, also known as Bosma arhinia microphthalmia syndrome (BAMS), is an extremely rare congenital condition characterized by the triad of complete absence of the nose (arhinia) or severe nasal hypoplasia, ocular defects (microphthalmia or anophthalmia), and hypogonadotropic hypogonadism. The condition is present from birth and affects multiple body systems including the craniofacial structures, the eyes, the olfactory system, and the reproductive endocrine axis. Patients typically have absent or severely underdeveloped external nasal structures, absent or rudimentary nasal passages, and absent paranasal sinuses. The olfactory system is affected, leading to hyposmia (reduced sense of smell) or anosmia (complete absence of smell). Eye abnormalities range from small eyes (microphthalmia) to absent eyes (anophthalmia), with variable degrees of visual impairment. Hypogonadotropic hypogonadism results from deficient gonadotropin-releasing hormone signaling, leading to delayed or absent puberty and potential infertility. The genetic basis of BAMS has been linked to mutations in the SMCHD1 gene, which plays a role in epigenetic regulation and chromatin organization. The condition appears to arise from de novo dominant mutations in most reported cases. Management is multidisciplinary and symptomatic, involving reconstructive craniofacial surgery to address nasal defects, ophthalmologic care for ocular abnormalities (including prosthetic eyes when needed), airway management, and hormone replacement therapy to induce puberty and address hypogonadism. Fertility treatment may be considered in adulthood. Due to the extreme rarity of this condition, with fewer than 50 cases reported in the medical literature, management is guided primarily by case reports and expert opinion rather than clinical trials.

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