PPP1R21 homozygous null variants associated with developmental delay, muscle weakness, distinctive facial features, and brain abnormalities.

We present 3 children with homozygous null variants in the PPP1R21 gene. A 3-year-old girl had profound developmental delay, hypotonia and weakness, poor feeding, recurrent chest infections and respiratory failure, rotatory nystagmus, absent reflexes, and a homozygous nonsense variant c.2089C>T (p.Arg697*). A 2-year-old boy had profound developmental delay, weakness and hypotonia, recurrent chest infections and respiratory distress, undescended testes, rotatory nystagmus, hyporeflexia, and a homozygous nonsense variant c.427C>T (p.Arg143*). An 11-year-old girl with profound developmental delay, weakness and hypotonia, stereotypic movements, growth failure, hyporeflexia, and a homozygous frameshift variant c.87_88delAG (p.Gly30Cysfs*4). In addition, these children shared common facial features (thick eyebrows, hypertelorism, broad nasal bridge, short nose with upturned nasal tip and broad low-hanging columella, thick lips, low-set ears, and coarse facies with excessive facial hair), and brain abnormalities (cerebellar vermis hypoplasia, ventricular dilatation, and reduced white matter volume). Although PPP1R21 has not yet been linked to human disease, the consistency in the phenotype of individuals from unrelated families, the nature of the variants which result in truncated proteins, and the expected vital role for PPP1R21 in cellular function, all support that PPP1R21 is a novel disease-associated gene responsible for the phenotype observed in these individuals.

TASP1 is deleted in an infant with developmental delay, microcephaly, distinctive facial features, and multiple congenital anomalies.

We report a 20p12.1 homozygous deletion including exons 5-10 of the TASP1 gene in an infant with developmental delay, acquired microcephaly, distinctive facial features, and multiple congenital anomalies involving skeletal, cardiac, and renal systems. TASP1 encodes taspase 1 which is responsible for cleaving, thus activating, a number of transcription factors including the mixed lineage leukemia 1 (MLL1). Taspase 1-deficient mice showed early lethality, skeletal abnormalities, and growth failure, which support a potentially causal role of TASP1 deletion in this infant. Furthermore, the infant reported here had many of the features seen in Wiedemann-Steiner syndrome which is caused by MLL1 defects. Such observation further supports that TASP1 is a novel disease-related gene that is associated with a disease phenotype overlapping with Wiedemann-Steiner syndrome as both are caused by defects in the same pathway.

Multiple sclerosis or "inflammatory CADASIL?": Case Report and review of the literature.

BACKGROUND: Multiple sclerosis (MS) and CADASIL presenting together is exceedingly rare. As more cases of "inflammatory" CADASIL emerge, diagnostic challenges for clinicians increase. We report an individual with MS and CADASIL presenting with cognitive decline at age 25. She presented with gadolinium enhancing lesions on MRI and inflammatory cerebrospinal fluid raising the question of whether these patients should be given a diagnosis of "inflammatory CADASIL" or both MS and CADASIL. METHODS: A literature review was conducted on reports of inflammatory CADASIL or MS and CADASIL, clinical presentations including spinal cord lesions and CSF inflammatory markers. RESULTS: Nine cases in the literature of individuals with CADASIL and inflammatory presentations were found with treatment varying from intravenous steroids to MS immunomodulatory therapy. CONCLUSIONS: If individuals with CADASIL present with immune mediated inflammatory components they may benefit from immunomodulatory therapy. This is discussed with a review of the inflammatory CADASIL/MS cases in the literature and report of a case.

WDR45B-related intellectual disability, spastic quadriplegia, epilepsy, and cerebral hypoplasia: A consistent neurodevelopmental syndrome.

The advancement in genomic sequencing has greatly improved the diagnostic yield for neurodevelopmental disorders and led to the discovery of large number of novel genes associated with these disorders. WDR45B has been identified as a potential intellectual disability gene through genomic sequencing of 2 large cohorts of affected individuals. In this report we present 6 individuals from 3 unrelated families with homozygous pathogenic variants in WDR45B: c.799C>T (p.Q267*) in 1 family and c.673C>T (p.R225*) in 2 families. These individuals shared a similar phenotype including profound development delay, early-onset refractory epilepsy, progressive spastic quadriplegia and contractures, and brain malformations. Neuroimaging showed ventriculomegaly, reduced cerebral white matter volume, and thinning of cerebral gray matter. The consistency in the phenotype strongly supports that WDR45B is associated with this disease.

Chromosomal microarray in a highly consanguineous population: diagnostic yield, utility of regions of homozygosity, and novel mutations.

Chromosomal microarray (CMA) has significantly improved diagnosing copy number variations (CNVs). Single nucleotide polymorphism (SNP) arrays confer additional utility in detecting regions of homozygosity (ROH). Investigating ROH for genes associated with recessive disorders for follow-up sequencing can aid in diagnosis. In this study, we performed a retrospective review of clinical and molecular data for 227 individuals from a highly consanguineous population who previously had a CMA. Pathogenic CNVs were identified in 32 (14%) cases; ROH suggesting uniparental disomy (UPD) in three (1%) cases, and an additional 25 (11%) individuals were diagnosed with recessive disorders caused by mutations in ROH candidate genes, thereby increasing the CMA diagnostic yield to 26%. Among the 25 individuals with recessive diseases, 18 had novel mutations in 16 genes (ASPM, SPINK5, QARS, MEGF10, SPATA7, GMPPA, ABCA4, SRD5A2, RPGRIP1L, MET, SLC12A6, ALDH1A3, TNFRSF11A, FLNB, PHGDH, and FKBP10) including five with phenotypic expansion.

FBXL4 defects are common in patients with congenital lactic acidemia and encephalomyopathic mitochondrial DNA depletion syndrome.

Mutations in FBXL4 have recently been recognized to cause a mitochondrial disorder, with clinical features including early onset lactic acidosis, hypotonia, and developmental delay. FBXL4 sequence analysis was performed in 808 subjects suspected to have a mitochondrial disorder. In addition, 28 samples from patients with early onset of lactic acidosis, but without identifiable mutations in 192 genes known to cause mitochondrial diseases, were examined for FBXL4 mutations. Definitive diagnosis was made in 10 new subjects with a total of 7 novel deleterious variants; 5 null and 2 missense substitutions. All patients exhibited congenital lactic acidemia, most of them with severe encephalopathic presentation, and global developmental delay. Overall, FBXL4 defects account for at least 0.7% (6 out of 808) of subjects suspected to have a mitochondrial disorder, and as high as 14.3% (4 out of 28) in young children with congenital lactic acidosis and clinical features of mitochondrial disease. Including FBLX4 in the mitochondrial diseases panel should be particularly important for patients with congenital lactic acidosis.

Microduplication of Xp11.23p11.3 with effects on cognition, behavior, and craniofacial development.

We report an ~1.3 Mb tandem duplication at Xp11.23p11.3 in an 11-year-old boy with pleasant personality, hyperactivity, learning and visual-spatial difficulties, relative microcephaly, long face, stellate iris pattern, and periorbital fullness. This clinical presentation is milder and distinct from that of patients with partially overlapping Xp11.22p11.23 duplications which have been described in males and females with intellectual disability, language delay, autistic behaviors, and seizures. The duplicated region harbors three known X-linked mental retardation genes: FTSJ1, ZNF81, and SYN1. Quantitative polymerase chain reaction from whole blood total RNA showed increased expression of three genes located in the duplicated region: EBP, WDR13, and ZNF81. Thus, over-expression of genes in the interval may contribute to the observed phenotype. Many of the features seen in this patient are present in individuals with Williams-Beuren syndrome (WBS). Interestingly, the SYN1 gene within the duplicated interval, as well as the STX1A gene, within the WBS critical region, co-localize to presynaptic active zones, and play important roles in neurotransmitter release.