Supplementary Material for: A Case of FAM111A-Associated Kenny–Caffey Syndrome Type 2 With New Clinical Features: Microtia, Lacunar Skull Appearance, and Arnold–Chiari Malformation

Introduction: Kenny–Caffey syndrome type 2 (KCS2, #OMIM127000) is an extremely rare skeletal dysplasia characterized by characteristic facial features, relative macrocephaly, short stature, hypoparathyroidism, hypocalcemia, cortical thickening of tubular bones, and medullary stenosis. It is caused by the Family with Sequence Similarity 111 Member A (FAM111A) gene. Case Presentation: Herein, we report a 7-year-old boy with microphthalmia, delayed anterior fontanelle closure, short stature, hypoparathyroidism, hypocalcemia, cortical thickening of tubular bones, and medullary stenosis. The presented patient had microcephaly, maculopathy, and craniosynostosis as rare distinct features. Microtia, lacunar skull appearance and Arnold-Chiari malformation were present only in the reported patient. A diagnosis of KCS2 was considered with the clinical and radiological findings. Whole exome sequencing identified a heterozygous pathogenic hotspot variant, c.1706G>A p.Arg569His (NM_001312909.2), in the FAM111A gene. Conclusion: Accurate diagnosis plays a critical role in enhancing clinical awareness, improving patient management, and offering appropriate genetic counseling for affected families.