Clin Genet. 2020 Sep;98(3):303-307. doi: 10.1111/cge.13805. PMID: 32617964.
In this case series, David et al. describe clinical features of 4 patients in 2 unrelated consanguineous families with TTC26 ciliopathy due to a homozygous c.695A>G p.Asn232Ser mutation. Three of the patients had MRI findings consistent with pituitary stalk interruption syndrome (PSIS), a congenital anomaly of the pituitary gland. Additionally, 2 of 3 patients with PSIS had multiple anterior pituitary hormone deficiency. Three patients also had ocular manifestations, including isolated bilateral esotropia, unilateral retinal coloboma, microphthalmia, corneal dystrophy, and optic disc edema, suggesting that ocular abnormalities are a part of the phenotype associated with defective TTC26.
Ciliopathies are a group of disorders characterized by impaired ciliary function and structure, and manifest in varying phenotypes. Recessively inherited mutations in TTC26 are known to cause severe biliary ciliopathy, and also involve other organ systems such as the brain, kidneys, and hearth. Although TTC26 is highly expressed in the pituitary and its deficiency dysregulates sonic hedgehog (SHH) signaling, the presence of pituitary gland involvement in ciliopathy caused by mutations in TTC26 has not been described before.
Altogether, this study describes a novel PSIS phenotype in patients with ciliopathy caused by mutations in TTC26. The findings support the view that cilia and SHH signaling are important in pituitary and ocular embryonic development.