OBJECTIVE: Aplasia of lacrimal and salivary glands (ALSG) is a syndromic disorder characterized by aplasia of lacrimal and salivary systems. Reported ophthalmic manifestations of ALSG include aplasia of lacrimal glands, punctal agenesis, lacrimal sac mucocele, and membranous congenital nasolacrimal duct obstruction (CNLDO). Bony CNLDO, a rare clinical entity, has not been associated with any syndromic disorder. This study investigated the relationship between genetic mutations and bony CNLDO in 3 Chinese families with ALSG.
METHODS: Single-center observational case study.
METHODS: Three Chinese families with bony CNLDO, including 7 affected and 9 healthy family members.
METHODS: Slit-lamp ophthalmic examination, comprehensive physical examination, orbital computed tomography (CT) imaging, cervicofacial magnetic resonance imaging, audiometry, and whole exome sequencing on periphery blood were performed. Variants were cross-referenced with 1000 control genomes and various population databases. Pathologic variants were identified using bioinformatic tools.
METHODS: Clinical examination, diagnostic imaging, whole exome sequencing, and bioinformatic analysis findings.
RESULTS: Affected patients showed decreased tear production on the Schimer I test and reduced tear breakup time. Bony CNLDO was observed on CT, showing unilateral or bilateral bony termination at the middle or terminal segment of the nasolacrimal canal. Magnetic resonance imaging showed aplasia or absence of lacrimal, parotid, and submandibular glands. Physical examination revealed normal ears, digits, and facial morphology. Audiometry and dental assessment were conducted on the pediatric patients and yielded normal results. The clinical characteristics of patients aligned with a diagnosis of ALSG. Genomic analysis revealed 3 novel heterozygous missense mutations of the Fgf10 gene: c.316T→C, c.327C→G, and c.332T→G. The inheritance pattern was autosomal dominant with variable penetrance. These variants were not observed in 1000 control genomes and population databases. These variant positions also were shown to be highly conserved across various animal species. Mutated genes and proteins were predicted as deleterious with most computational models, with a few suggesting they may be benign.
CONCLUSIONS: Bony CNLDO was identified as a novel phenotype of ALSG implicated by missense mutations of highly conserved residues in the Fgf10 gene. These cases broadened our knowledge of Fgf10-related phenotypes and prompted clinicians to consider syndromic associations in patients with bony CNLDO.
BACKGROUND: The author(s) have no proprietary or commercial interest in any materials discussed in this article.

Thirteen affected individuals of six generations of a single kindred presented with epiphora evident from infancy. Physical exam and Schirmer test revealed variable expression of tear deficiency, congenital punctal atresia, and dry mouth with multiple caries, without concomitant abnormalities of the ears or digits, commensurate with a diagnosis of aplasia of the lacrimal and salivary glands (ALSG). Reconstruction of the upper lacrimal drainage system was performed in some of the affected individuals. Genetic analysis, testing six affected individuals and three non-affected family members, identified a single novel heterozygous splice-site variant, c.429 + 1, G > T in fibroblast growth factor 10 (FGF10) (NM_004465.1), segregating throughout the family as expected for dominant heredity. RT-PCR assays of HEK-293 cells transfected with wild type or mutant FGF10 demonstrated that the variant causes skipping of Exon 2. Notably, individuals sharing the same variant exhibited phenotypic variability, with unilateral or bilateral epiphora, as well as variable expression of dry mouth and caries. Moreover, one of the variant carriers had no ALSG-related clinical findings, demonstrating incomplete penetrance. While coding mutations in FGF10 are known to cause malformations in the nasolacrimal system, this is the second FGF10 splice-site variant and the first donor-site variant reported to cause ALSG. Thus, our study of a unique large kindred with multiple affected individuals heterozygous for the same FGF10 variant highlights intronic splice-site mutations and phenotypic variability/partial penetrance in ALSG.

Aplasia/agenesis of lacrimal and salivary glands is a rare congenital defect that has been associated with disturbances in fibroblast growth factor 10 (FGF10). It can present with symptoms of congenital lacrimal obstruction, dry eye, and dry mouth. We report the ophthalmological and genetic study of a 19-year-old woman and her relatives suffering from this syndrome. A new probably pathogenic variant is described in the FGF10 gene.