Split-hand/foot malformation (SHFM) is a rare congenital limb anomaly defined by the absence or hypoplasia of the central rays of the autopod. SHFM occurs as an isolated entity or part of genetic syndromes with several causative copy-number variations or monogenic alterations known to be involved in the disease pathomechanism. On the other hand, cleft lip/palate (CL/P) usually results from polygenic and environmental factors, with the complex interplay of both leading to this malformation. Pathogenic variants in FGFR1 have been linked to phenotypically distinct disorders, including Hartsfield syndrome, Kallmann syndrome, Jackson-Weiss syndrome, osteoglophonic dysplasia, and Pfeiffer syndrome. Although pathogenic variants in FGFR1 can contribute to syndromic SHFM or CL/P, their role in isolated SHFM or CL remains poorly described in the literature. We conducted targeted next-generation sequencing (NGS) in the proband with SHFM, followed by segregation analysis in the family members. In this study, we report an index patient presenting with isolated SHFM and his brother with CL and facial dysmorphism, as well as their father with isolated hyposmia. Targeted next-generation sequencing revealed a previously reported heterozygous missense pathogenic variant in FGFR1 (c.830G>A; p.Cys277Tyr) in both affected siblings and their hyposmic father. This study expands the phenotypic spectrum associated with FGFR1 pathogenic variants, emphasizing their involvement in non-syndromic SHFM and CL or isolated hyposmia. Our findings highlight the importance of considering FGFR1 in the molecular diagnosis of isolated SHFM or orofacial clefting, point to the high intrafamilial variability of FGFR1 pathogenic variants, and demonstrate the diagnostic value of targeted NGS in rare congenital malformations.

Crouzon syndrome is a rare form of syndromic craniosynostosis (SC) characterized by premature fusion of the cranial and facial sutures, elevated intracranial pressure, varying degrees of ocular exposure due to exorbitism, and airway compromise caused by midface retrusion. Craniolacunae and upper and lower extremity anomalies are not frequently found in Crouzon syndrome. We present a girl with Crouzon syndrome caused by c.1040 C > G, p.Ser347Cys, a pathogenic mutation in the FGFR2 gene with atypical characteristics, including craniolacunae resembling severe Swiss cheese type of bone formation, and upper and lower extremity anomalies which are more commonly associated with Pfeiffer syndrome patients. Distinguishing between severe Crouzon syndrome patients and patients who have mild and/or moderate Pfeiffer syndrome can be challenging even for an experienced craniofacial surgeon. An accurate genotype diagnosis is essential to distinguishing between these syndromes, as it provides predictors for neurosurgical complications and facilitates appropriate family counseling related to long-term outcomes.

Patients with syndromic craniosynostosis (CS) can present with both intracranial and extracranial manifestations. Extracranial features include proptosis, exorbitism, and midface hypoplasia. Intracranial manifestations can include elevated intracranial pressure (ICP), brainstem compression, foramen magnum stenosis or jugular foramen hypoplasia with resultant venous hypertension and anomalous drainage. While fronto-orbital advancement, cranial vault remodeling, and posterior fossa decompression are standard surgical approaches to normalizing orbito-cranial volume and morphology, associated hydrocephalus, anomalous venous drainage, and tonsillar herniation often affect the timing, safety, and selection of corrective interventions. The surgical decision-making to circumvent venous emissaries, effectively time treatment of hydrocephalus, and address posterior versus anterior pathology primarily has not been widely described in the literature, and is important in the development of guidelines in these complex cases. In this report, we describe the surgical management of a patient with Jackson-Weiss syndrome presenting with delayed, but rapidly progressive bilateral lambdoid CS, severe proptosis, midface hypoplasia, elevated ICP, hydrocephalus, tonsillar ectopia, and severe venous hypertension with anomalous drainage. We review the literature related to management of complex synostosis and present our surgical decision-making in the setting of complex syndromic synostosis to aid in the formation of guidelines toward approaching these cases.

Hartsfield syndrome is a rare clinical entity characterized by holoprosencephaly and ectrodactyly with the variable feature of cleft lip/palate. In addition to these symptoms patients with Hartsfield syndrome can show developmental delay of variable severity, isolated hypogonadotropic hypogonadism, central diabetes insipidus, vertebral anomalies, eye anomalies, and cardiac malformations. Pathogenic variants in FGFR1 have been described to cause phenotypically different FGFR1-related disorders such as Hartsfield syndrome, hypogonadotropic hypogonadism with or without anosmia, Jackson-Weiss syndrome, osteoglophonic dysplasia, Pfeiffer syndrome, and trigonocephaly Type 1. Here, we report three patients with Hartsfield syndrome from two unrelated families. Exome sequencing revealed two siblings harboring a novel de novo heterozygous synonymous variant c.1029G>A, p.Ala343Ala causing a cryptic splice donor site in exon 8 of FGFR1 likely due to gonadal mosaicism in one parent. The third case was a sporadic patient with a novel de novo heterozygous missense variant c.1868A>G, p.(Asp623Gly).

Little is currently known about the mechanisms by which pathogenic variants of FGFR2 produce changes in the FGFR protein and influence the clinical presentation of affected individuals. We report on a patient with a de novo pathogenic variant of FGFR2 and a phenotype consistent with Jackson-Weiss syndrome who presented with delayed, rapidly progressive multisutural craniosynostosis and associated medical complications. Using 3-dimensional modeling of the FGFR protein, we provide evidence that this variant resulted in abnormal dimerization and constitutive activation of FGFR, leading to the Jackson-Weiss phenotype. Knowledge regarding the correlation between genotype and phenotype of persons with FGFR2-related craniosynostosis has the potential to allow for anticipation of medical complications, institution of early treatment, and improved clinical outcomes.