Benefit of 5 years of enzyme replacement therapy in advanced late onset Pompe. A case report of misdiagnosis for three decades with acute respiratory failure at presentation.

We report on a 57 year old female patient who presented in acute respiratory failure with severe generalized weakness. She was previously misdiagnosed for over three decades as polymyositis. She was treated with enzyme replacement therapy (ERT) for over five years, after being diagnosed with late onset Pompe Disease (LOPD). She returned to independent living with the use of non invasive ventilation at nights. ERT should be considered in the management of patients with advanced LOPD and the effects of ERT closely monitored.

Biallelic Variants in the Ectonucleotidase ENTPD1 Cause a Complex Neurodevelopmental Disorder with Intellectual Disability, Distinct White Matter Abnormalities, and Spastic Paraplegia.

OBJECTIVE: Human genomics established that pathogenic variation in diverse genes can underlie a single disorder. For example, hereditary spastic paraplegia is associated with >80 genes, with frequently only few affected individuals described for each gene. Herein, we characterize a large cohort of individuals with biallelic variation in ENTPD1, a gene previously linked to spastic paraplegia 64 (Mendelian Inheritance in Man # 615683). METHODS: Individuals with biallelic ENTPD1 variants were recruited worldwide. Deep phenotyping and molecular characterization were performed. RESULTS: A total of 27 individuals from 17 unrelated families were studied; additional phenotypic information was collected from published cases. Twelve novel pathogenic ENTPD1 variants are described (NM 001776.6): c.398_399delinsAA; p.(Gly133Glu), c.540del; p.(Thr181Leufs*18), c.640del; p.(Gly216Glufs*75), c.185 T > G; p.(Leu62*), c.1531 T > C; p.(*511Glnext*100), c.967C > T; p.(Gln323*), c.414-2_414-1del, and c.146 A > G; p.(Tyr49Cys) including 4 recurrent variants c.1109 T > A; p.(Leu370*), c.574-6_574-3del, c.770_771del; p.(Gly257Glufs*18), and c.1041del; p.(Ile348Phefs*19). Shared disease traits include childhood onset, progressive spastic paraplegia, intellectual disability (ID), dysarthria, and white matter abnormalities. In vitro assays demonstrate that ENTPD1 expression and function are impaired and that c.574-6_574-3del causes exon skipping. Global metabolomics demonstrate ENTPD1 deficiency leads to impaired nucleotide, lipid, and energy metabolism. INTERPRETATION: The ENTPD1 locus trait consists of childhood disease onset, ID, progressive spastic paraparesis, dysarthria, dysmorphisms, and white matter abnormalities, with some individuals showing neurocognitive regression. Investigation of an allelic series of ENTPD1 (1) expands previously described features of ENTPD1-related neurological disease, (2) highlights the importance of genotype-driven deep phenotyping, (3) documents the need for global collaborative efforts to characterize rare autosomal recessive disease traits, and (4) provides insights into disease trait neurobiology. ANN NEUROL 2022;92:304-321.

Case Report of Cardiac Arrest After Succinylcholine in a Child With Muscle-Eye-Brain Disease.

Muscle-eye-brain disease is a rare autosomal recessive disorder characterized by congenital muscular dystrophy, ocular abnormalities, and brain malformation. We report an intraoperative hyperkalemic cardiac arrest following the administration of succinylcholine in a child with muscle-eye-brain disease. The disease was diagnosed only after this event. Our experience suggests that preoperative determinations of serum concentrations of lactate and creatine kinase may be useful if clinical signs consistent with myopathy are present.

The clinical application of genome-wide sequencing for monogenic diseases in Canada: Position Statement of the Canadian College of Medical Geneticists.

PURPOSE AND SCOPE: The aim of this Position Statement is to provide recommendations for Canadian medical geneticists, clinical laboratory geneticists, genetic counsellors and other physicians regarding the use of genome-wide sequencing of germline DNA in the context of clinical genetic diagnosis. This statement has been developed to facilitate the clinical translation and development of best practices for clinical genome-wide sequencing for genetic diagnosis of monogenic diseases in Canada; it does not address the clinical application of this technology in other fields such as molecular investigation of cancer or for population screening of healthy individuals. METHODS OF STATEMENT DEVELOPMENT: Two multidisciplinary groups consisting of medical geneticists, clinical laboratory geneticists, genetic counsellors, ethicists, lawyers and genetic researchers were assembled to review existing literature and guidelines on genome-wide sequencing for clinical genetic diagnosis in the context of monogenic diseases, and to make recommendations relevant to the Canadian context. The statement was circulated for comment to the Canadian College of Medical Geneticists (CCMG) membership-at-large and, following incorporation of feedback, approved by the CCMG Board of Directors. The CCMG is a Canadian organisation responsible for certifying medical geneticists and clinical laboratory geneticists, and for establishing professional and ethical standards for clinical genetics services in Canada. RESULTS AND CONCLUSIONS: Recommendations include (1) clinical genome-wide sequencing is an appropriate approach in the diagnostic assessment of a patient for whom there is suspicion of a significant monogenic disease that is associated with a high degree of genetic heterogeneity, or where specific genetic tests have failed to provide a diagnosis; (2) until the benefits of reporting incidental findings are established, we do not endorse the intentional clinical analysis of disease-associated genes other than those linked to the primary indication; and (3) clinicians should provide genetic counselling and obtain informed consent prior to undertaking clinical genome-wide sequencing. Counselling should include discussion of the limitations of testing, likelihood and implications of diagnosis and incidental findings, and the potential need for further analysis to facilitate clinical interpretation, including studies performed in a research setting. These recommendations will be routinely re-evaluated as knowledge of diagnostic and clinical utility of clinical genome-wide sequencing improves. While the document was developed to direct practice in Canada, the applicability of the statement is broader and will be of interest to clinicians and health jurisdictions internationally.

Meier-Gorlin syndrome: growth and secondary sexual development of a microcephalic primordial dwarfism disorder.

Meier-Gorlin syndrome (MGS) is a rare autosomal recessive disorder characterized by primordial dwarfism, microtia, and patellar aplasia/hypoplasia. Recently, mutations in the ORC1, ORC4, ORC6, CDT1, and CDC6 genes, encoding components of the pre-replication complex, have been identified. This complex is essential for DNA replication and therefore mutations are expected to impair cell proliferation and consequently could globally reduce growth. However, detailed growth characteristics of MGS patients have not been reported, and so this is addressed here through study of 45 MGS patients, the largest cohort worldwide. Here, we report that growth velocity (length) is impaired in MGS during pregnancy and first year of life, but, thereafter, height increases in paralleled normal reference centiles, resulting in a mean adult height of -4.5 standard deviations (SD). Height is dependent on ethnic background and underlying molecular cause, with ORC1 and ORC4 mutations causing more severe short stature and microcephaly. Growth hormone therapy (n = 9) was generally ineffective, though in two patients with significantly reduced IGF1 levels, growth was substantially improved by GH treatment, with 2SD and 3.8 SD improvement in height. Growth parameters for monitoring growth in future MGS patients are provided and as well we highlight that growth is disproportionately affected in certain structures, with growth related minor genital abnormalities (42%) and mammary hypoplasia (100%) frequently present, in addition to established effects on ears and patellar growth.

Meier-Gorlin syndrome genotype-phenotype studies: 35 individuals with pre-replication complex gene mutations and 10 without molecular diagnosis.

Meier-Gorlin syndrome (MGS) is an autosomal recessive disorder characterized by microtia, patellar aplasia/hypoplasia, and short stature. Recently, mutations in five genes from the pre-replication complex (ORC1, ORC4, ORC6, CDT1, and CDC6), crucial in cell-cycle progression and growth, were identified in individuals with MGS. Here, we report on genotype-phenotype studies in 45 individuals with MGS (27 females, 18 males; age 3 months-47 years). Thirty-five individuals had biallelic mutations in one of the five causative pre-replication genes. No homozygous or compound heterozygous null mutations were detected. In 10 individuals, no definitive molecular diagnosis was made. The triad of microtia, absent/hypoplastic patellae, and short stature was observed in 82% of individuals with MGS. Additional frequent clinical features were mammary hypoplasia (100%) and abnormal genitalia (42%; predominantly cryptorchidism and hypoplastic labia minora/majora). One individual with ORC1 mutations only had short stature, emphasizing the highly variable clinical spectrum of MGS. Individuals with ORC1 mutations had significantly shorter stature and smaller head circumferences than individuals from other gene categories. Furthermore, compared with homozygous missense mutations, compound heterozygous mutations appeared to have a more severe effect on phenotype, causing more severe growth retardation in ORC4 and more frequently pulmonary emphysema in CDT1. A lethal phenotype was seen in four individuals with compound heterozygous ORC1 and CDT1 mutations. No other clear genotype-phenotype association was observed. Growth hormone and estrogen treatment may be of some benefit, respectively, to growth retardation and breast hypoplasia, though further studies in this patient group are needed.

Further expansion of the phenotypic spectrum associated with mutations in ALDH18A1, encoding Δ¹-pyrroline-5-carboxylate synthase (P5CS).

We report on the third case of cutis laxa and progeroid features caused by a homozygous mutation in ALDH18A1 that encodes Δ¹-pyrroline-5-carboxylate-synthase (P5CS). This severely affected child, born to consanguineous parents of Pakistani origin, presented with lax, wrinkled and thin skin with dilated and tortuous subcutaneous blood vessels, corneal clouding, and hypotonia. The child had severe global developmental delay and feeding difficulties and died in infancy for an unknown reason. The proband was homozygous for a mutation in ALDH18A1, c.1923 + 1G > A which results in the production of two anomalous transcripts that are predicted to encode proteins lacking the catalytic site for the enzyme. The cellular phenotype is characterized by diminished production of collagen types I and III, altered elastin ultrastructure, and diminished cell proliferation of cultured dermal fibroblasts. This severe clinical and cellular phenotype overlaps with a broad group of neurocutaneous syndromes that include cutis laxa type II, wrinkly skin syndrome, de Barsy syndrome, and gerodermia osteodysplastica. The findings presented here emphasize the pleiotropic presentation of this group of conditions and suggest that multiple components of the extracellular matrix are perturbed in these disorders.

Mutations in origin recognition complex gene ORC4 cause Meier-Gorlin syndrome.

Meier-Gorlin syndrome is a rare autosomal recessive genetic condition whose primary clinical hallmarks include small stature, small external ears and small or absent patellae. Using marker-assisted mapping in multiple families from a founder population and traditional coding exon sequencing of positional candidate genes, we identified three different mutations in the gene encoding ORC4, a component of the eukaryotic origin recognition complex, in five individuals with Meier-Gorlin syndrome. In two such individuals that were negative for mutations in ORC4, we found potential mutations in ORC1 and CDT1, two other genes involved in origin recognition. ORC4 is well conserved in eukaryotes, and the yeast equivalent of the human ORC4 missense mutation was shown to be pathogenic in functional assays of cell growth. This is the first report, to our knowledge, of a germline mutation in any gene of the origin recognition complex in a vertebrate organism.

Mutation in the gene encoding ubiquitin ligase LRSAM1 in patients with Charcot-Marie-Tooth disease.

Charcot-Marie-Tooth disease (CMT) represents a family of related sensorimotor neuropathies. We studied a large family from a rural eastern Canadian community, with multiple individuals suffering from a condition clinically most similar to autosomal recessive axonal CMT, or AR-CMT2. Homozygosity mapping with high-density SNP genotyping of six affected individuals from the family excluded 23 known genes for various subtypes of CMT and instead identified a single homozygous region on chromosome 9, at 122,423,730-129,841,977 Mbp, shared identical by state in all six affected individuals. A homozygous pathogenic variant was identified in the gene encoding leucine rich repeat and sterile alpha motif 1 (LRSAM1) by direct DNA sequencing of genes within the region in affected DNA samples. The single nucleotide change mutates an intronic consensus acceptor splicing site from AG to AA. Direct analysis of RNA from patient blood demonstrated aberrant splicing of the affected exon, causing an obligatory frameshift and premature truncation of the protein. Western blotting of immortalized cells from a homozygous patient showed complete absence of detectable protein, consistent with the splice site defect. LRSAM1 plays a role in membrane vesicle fusion during viral maturation and for proper adhesion of neuronal cells in culture. Other ubiquitin ligases play documented roles in neurodegenerative diseases. LRSAM1 is a strong candidate for the causal gene for the genetic disorder in our kindred.

OBSL1 mutations in 3-M syndrome are associated with a modulation of IGFBP2 and IGFBP5 expression levels.

3-M syndrome is an autosomal recessive disorder characterized by severe pre- and postnatal growth retardation and minor skeletal changes. We have previously identified CUL7 as a disease-causing gene but we have also provided evidence of genetic heterogeneity in the 3-M syndrome. By homozygosity mapping in two inbred families, we found a second disease locus on chromosome 2q35-36.1 in a 5.2-Mb interval that encompasses 60 genes. To select candidate genes, we performed microarray analysis of cultured skin fibroblast RNA from one patient, looking for genes with altered expression; we found decreased expression of IGFBP2 and increased expression of IGFBP5. However, direct sequencing of these two genes failed to detect any anomaly. We then considered other candidate genes by their function/location and found nine distinct mutations in the OBSL1 gene in 13 families including eight nonsense and one missense mutations. To further understand the links between OBSL1, CUL7, and insulin-like growth factor binding proteins (IGFBPs), we performed real-time quantitative PCR (RT-PCR) analysis for OBSL1, CUL7, IGFBP2, and IGFBP5, using cultured fibroblast RNAs from two patients with distinct OBSL1 mutations (p.F697G; p.H814RfsX15). We found normal CUL7 mRNA levels but abnormal IGFBP2 and IGFBP5 mRNA levels in the two patients, suggesting that OBSL1 modulates the expression of IGFBP proteins.

Prenatal diagnosis of Apert syndrome: report of two cases.

Two de novo cases with Apert Syndrome detected prenatally are presented herein. In the first, fetal ultrasound findings of syndactyly of the hands, craniosynostosis and proptosis resulted in a prenatal diagnosis in the nineteenth week of gestation. This is the earliest prenatal diagnosis of this syndrome in a not-at-risk case. Following counseling, this pregnancy was terminated and subsequent pathological examination and DNA analysis confirmed the diagnosis of Apert Syndrome and coarctation of the aorta. In the second case, fetal ultrasound at 21 weeks' gestation revealed a hypoplastic left heart and clover-leaf skull. Following counseling, this pregnancy was also terminated. Further examination of the fetus and DNA analysis led to a diagnosis of Apert Syndrome. These cases emphasize the need to complete a thorough fetal ultrasound in cases with potentially lethal cardiac abnormality and the importance of incorporating a fetal pathologist, as well as a medical geneticist, in the investigations performed after delivery or pregnancy termination when a fetal abnormality is detected on ultrasound.