Novel sonic hedgehog gene variant in a patient with hyponatremia, microsomia, and midline defects; phenotype description in association with a variant of unknown significance [c.755_757del p.(Phe252del)] and an approach to salt-wasting in SHH-related adrenal disorders

Objectives: To contribute a novel sonic hedgehog (SHH) gene variant in association with a novel-meagerly described phenotype and discuss SHH signaling pathway pathology.

Case presentation: We present a 5-year-old boy with excessive hyponatremia and natriuresis, microform holoprosencephaly and microsomia, with morphologically intact hypothalamic-pituitary-adrenal (HPA) axis, and hypoaldosteronism, yet without hyperreninemia, hyperkalemia, dehydration episodes, or glucocorticoid insufficiency. Extensive workup excluded common causes of salt-wasting and revealed a novel variant of unknown significance on the sonic hedgehog (SHH) gene; NM_000193.4:c.755_757del (p.Phe252del), in heterozygosity.

Conclusions: Salt-wasting in children is predominantly caused by central nervous system lesions, renal tubular dysfunction, or adrenal insufficiency. The SHH protein is a signaling molecule, essential in embryogenesis-including HPA axis differentiation. Inactivating SHH variants disrupt the signaling pathway, leading to dysplasia or dysfunction of target organs. What's new: • We analyze the patient's phenotype in the light of this novel variant • Patient's isolated aldosterone deficiency possibly implies a selective signaling defect affecting the development of adrenal zona glomerulosa • Unexplained hyporeninemia and hypokalemia in the context of hypoaldosteronism raise questions on SHH signaling pathophysiology.