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Rationale: Familial recurrence studies provide strong evidence for a genetic component to the predisposition to sporadic, nonsyndromic Tetralogy of Fallot (TOF), the most common cyanotic congenital heart disease phenotype. Rare genetic variants have been identified as important contributors to the risk of congenital heart disease, but relatively small numbers of TOF cases have been studied to date., Objective: We used whole exome sequencing to assess the prevalence of unique, deleterious variants in the largest cohort of nonsyndromic TOF patients reported to date., Methods and Results: Eight hundred twenty-nine TOF patients underwent whole exome sequencing. The presence of unique, deleterious variants was determined; defined by their absence in the Genome Aggregation Database and a scaled combined annotation-dependent depletion score of ≥20. The clustering of variants in 2 genes, NOTCH1 and FLT4, surpassed thresholds for genome-wide significance (assigned as P<5×10 -8 ) after correction for multiple comparisons. NOTCH1 was most frequently found to harbor unique, deleterious variants. Thirty-one changes were observed in 37 probands (4.5%; 95% CI, 3.2%-6.1%) and included 7 loss-of-function variants 22 missense variants and 2 in-frame indels. Sanger sequencing of the unaffected parents of 7 cases identified 5 de novo variants. Three NOTCH1 variants (p.G200R, p.C607Y, and p.N1875S) were subjected to functional evaluation, and 2 showed a reduction in Jagged1-induced NOTCH signaling. FLT4 variants were found in 2.4% (95% CI, 1.6%-3.8%) of TOF patients, with 21 patients harboring 22 unique, deleterious variants. The variants identified were distinct to those that cause the congenital lymphoedema syndrome Milroy disease. In addition to NOTCH1, FLT4 and the well-established TOF gene, TBX1, we identified potential association with variants in several other candidates, including RYR1, ZFPM1, CAMTA2, DLX6, and PCM1., Conclusions: The NOTCH1 locus is the most frequent site of genetic variants predisposing to nonsyndromic TOF, followed by FLT4. Together, variants in these genes are found in almost 7% of TOF patients.

The objective of this study was to report the clinical and biological characteristics of two Perrault syndrome cases in a Moroccan family with homozygous variant c.1565C>A in the LARS2 gene and to establish genotype-phenotype correlation of patients with the same mutation by review of the literature. Whole-exome sequencing was performed. Data analysis was carried out and confirmed by Sanger sequencing and segregation. The affected siblings were diagnosed as having Perrault syndrome with sensorineural hearing loss at low frequencies; the female proband had primary amenorrhea and ovarian dysgenesis. Both affected individuals had a marfanoid habitus and no neurological features. Both patients carried the homozygous variant c.1565C>A; p.Thr522Asn in exon 13 of the LARS2 gene. This variant has already been reported as a homozygous variant in three other Perrault syndrome families. Both affected siblings of a Moroccan consanguineous family with LARS2 variants had low-frequency sensorineural hearing loss, marfanoid habitus, and primary ovarian insufficiency in the affected girl. According to the literature, this variant, c.1565C>A; p.Thr522Asn, can be correlated with low-frequency hearing loss. However, marfanoid habitus was been considered a nonspecific feature in Perrault syndrome, but we believe that it may be more specific than considered previously. This diagnosis allowed us to provide appropriate management to the patients and to provide more accurate genetic counseling to this family.

Objectives: We aimed to determine the proportion of individuals in our schwannomatosis cohort whose disease is associated with an LZTR1 mutation., Methods: We used exome sequencing, Sanger sequencing, and copy number analysis to screen 65 unrelated individuals with schwannomatosis who were negative for a germline NF2 or SMARCB1 mutation. We also screened samples from 39 patients with a unilateral vestibular schwannoma (UVS), plus at least one other schwannoma, but who did not have an identifiable germline or mosaic NF2 mutation., Results: We identified germline LZTR1 mutations in 6 of 16 patients (37.5%) with schwannomatosis who had at least one affected relative, 11 of 49 (22%) sporadic patients, and 2 of 39 patients with UVS in our cohort. Three germline mutation-positive patients in total had developed a UVS. Mosaicism was excluded in 3 patients without germline mutation in NF2, SMARCB1, or LZTR1 by mutation screening in 2 tumors from each., Conclusions: Our data confirm the relationship between mutations in LZTR1 and schwannomatosis. They indicate that germline mutations in LZTR1 confer an increased risk of vestibular schwannoma, providing further overlap with NF2, and that further causative genes for schwannomatosis remain to be identified., (© 2014 American Academy of Neurology.)

Summary: We report case of an infant who presented with failure to thrive and developmental delay at 4 months of age. He was diagnosed to have vitamin B12 deficiency and antibodies to intrinsic factor secondary to undiagnosed maternal pernicious anemia. The child was treated with hydroxocobalamin and now at 2 years of age, he is developing and growing within normal range. We review the literature on this rare cause of cobalamin deficiency in infants. We highlight the factors determining the outcome and situations where raised index of suspicion could help in recognizing this preventable cause of developmental delay and learning difficulties.