Genetic Variability of SOX10 -Related Disorders within an Italian Family: Straddling the Line between Kallmann and Waardenburg Syndrome

Introduction: Kallmann syndrome (KS) is a genetically heterogeneous developmental disorder that most often manifests hypogonadotropic hypogonadism (HH) and hypo-/anosmia due to early embryonic impairment in the migration of gonadotropin-releasing hormone neurons. SOX10 (SRY-Box 10; MIM∗602229), a key transcriptional activator involved in the development of neural crest cells, has been associated with KS and is identified as one of the causative genes of Waardenburg syndrome (WS). Case Presentation: A 28-year-old female patient, who was clinically diagnosed with KS in her childhood, presented with HH and anosmia, mild bilateral sensorineural hearing loss (SNHL), and pigmentation abnormalities. Next-generation sequencing analysis detected a missense heterozygous SOX10 pathogenic variant (NM_006941.4:c.506C>T) in the proposita and in her mother, whose phenotype included exclusively anosmia and hypopigmented skin patches. The same variant has been described by Pingault et al. [Clin Genet. 2015;88(4):352-9] in a patient with apparently isolated bilateral severe SNHL. Conclusion: Our finding substantiates the extreme phenotypic variability of SOX10-related disorders, which range from classical KS and/or WS to contracted endophenotypes that could share a common pathway in the development of neural crest cells and highlights the need for careful evaluation and longterm follow-up of SOX10 patients, with special focus on atypical/additional and/or late-onset phenotypic traits.