Phenotypic expansion in KIF1A-related dominant disorders: A description of novel variants and review of published cases.

KIF1A is a molecular motor for membrane-bound cargo important to the development and survival of sensory neurons. KIF1A dysfunction has been associated with several Mendelian disorders with a spectrum of overlapping phenotypes, ranging from spastic paraplegia to intellectual disability. We present a novel pathogenic in-frame deletion in the KIF1A molecular motor domain inherited by two affected siblings from an unaffected mother with apparent germline mosaicism. We identified eight additional cases with heterozygous, pathogenic KIF1A variants ascertained from a local data lake. Our data provide evidence for the expansion of KIF1A-associated phenotypes to include hip subluxation and dystonia as well as phenotypes observed in only a single case: gelastic cataplexy, coxa valga, and double collecting system. We review the literature and suggest that KIF1A dysfunction is better understood as a single neuromuscular disorder with variable involvement of other organ systems than a set of discrete disorders converging at a single locus.

Syndromic and Systemic Diagnoses Associated With Isolated Sagittal Synostosis.

Reports of systemic associations in patients with Isolated Sagittal Synostosis (ISS) are sparse. Craniofacial surgeons, and other providers, should be aware that a significant proportion of patients with ISS may have syndromic or systemic involvement. This study investigates the incidence of systemic disease and syndromic diagnosis in a cohort of patients presenting with ISS (ie, patients with sagittal synostosis without other sutural involvement). METHODS: This study consists of a retrospective review of patients diagnosed with ISS between 2007 and 2017 at a single institution. Patients were divided according to onset (early <1 year, late >1 year) of ISS. Patient notes were examined for congenital anomalies, systemic conditions, and molecular testing. Only patients with isolated sagittal fusion-meaning, patients with sagittal synostosis and no other sutural involvement-were included. RESULTS: Three hundred seventy-seven patients met the inclusion criteria: systemic conditions were identified in 188/377 (50%) of them. One hundred sixty-one patients with early onset (Group A), and 216 patients with late onset ISS (Group B) were identified. Systemic involvement was identified in 38% of Group A and 60% of Group B, which was statistically significant (P < 0.001). Forty-eight of 377 (13%) of patients had a syndromic diagnosis, and 79% of these were confirmed via genetic testing. Thirty-five percent of patients were diagnosed with central nervous system anomalies and 16% had craniofacial anomalies. CONCLUSIONS: Nearly 50% of the patients initially diagnosed with ISS were found to have some form of systemic involvement. This supports affording full pediatric and genetic evaluation with molecular testing to these children.

Co-existence of 9p deletion and Silver-Russell syndromes in a patient with maternally inherited cryptic complex chromosome rearrangement involving chromosomes 4, 9, and 11.

We report a patient with a maternally inherited unbalanced complex chromosomal rearrangement (CCR) involving chromosomes 4, 9, and 11 detected by microarray comparative genomic hybridization (aCGH) and fluorescence in situ hybridization (FISH). This patient presents with clinical features of 9p deletion syndrome and Silver-Russell syndrome (SRS). Chromosome analysis performed in 2000 showed what appeared to be a simple terminal deletion of chromosome 9p22.1. aCGH performed in 2010 revealed a 1.63 Mb duplication at 4q28.3, a 15.48 Mb deletion at 9p24.3p22.3, and a 1.95 Mb duplication at 11p15.5. FISH analysis revealed a derivative chromosome 9 resulting from an unbalanced translocation between chromosomes 9 and 11, a chromosome 4 fragment inserted near the breakpoint of the translocation. The 4q28.3 duplication does not contain any currently known genes. The 9p24.3p22.3 deletion region contains 36 OMIM genes including a 3.5 Mb critical region for the 9p-phenotype. The 11p15.5 duplication contains 49 OMIM genes including H19 and IGF2. Maternal aCGH was normal. However, maternal chromosomal and FISH analyses revealed an apparently balanced CCR involving chromosomes 4, 9, and 11. To the best of our knowledge, this is the first report of a patient with maternally inherited trans-duplication of the entire imprinting control region 1 (ICR1) among the 11p15.5 duplications reported in SRS patients. This report supports the hypothesis that the trans-duplication of the maternal copy of ICR1 alone is sufficient for the clinical manifestation of SRS and demonstrates the usefulness of combining aCGH with karyotyping and FISH for detecting cryptic genomic imbalances.