A PMM2-CDG caused by an A108V mutation associated with a heterozygous 70 kilobases deletion case report

Background

Congenital Disorders of Glycosylation (CDG) are a large group of inborn errors of metabolism with more than 140 different CDG types reported to date (1). The first characterized, PMM2-CDG, with an autosomal recessive transmission, is also the most frequent. The PMM2 gene encodes a phosphomannomutase. Here, a novel genetic variation causing PMM2-CDG is reported. 

Case presentation

We report the case of a French child, from healthy and unrelated parents, presenting congenital ataxia with hypotonia, hyperlaxity, inverted nipples, as well as altered coagulation parameters and liver function. Transferrin isoelectrofocusing revealed a typical type I CDG profile. Direct Sanger sequencing and quantitative PCR of PMM2 revealed a unique and novel genotype. On one allele, the patient was heterozygote with a known missense variant NM_000303.3(PMM2):c.323C > T, p.Ala108Val in exon 4. On the second allele, whole genome sequencing (WGS) indicated the presence of a novel heterozygous 70 kb deletion.

Conclusion

We report in the present paper the largest known heterozygous deletion of a PMM2 gene. The observation reveals the impact of a precise diagnostic on genetic counselling: by using WGS, an erroneous conclusion of homozygosity in the case of a relatively rare variant could be avoided, and an index patient with healthy and unrelated parents correctly identified.

Biometry of the Cerebellar Vermis and Brain Stem in Children: MR Imaging Reference Data from Measurements in 718 Children

BACKGROUND AND PURPOSE

Objective and quantitative data to define cerebellar vermis and/or brain stem hypoplasia in children are lacking. Our aim was to provide MR imaging biometric references for the cerebellar vermis and brain stem from a large cohort of children with normal cerebellums.

MATERIALS AND METHODS

The MR imaging data were retrospectively selected from our hospital data base from January 1, 2014, to December 31, 2017. All MR imaging examinations of children between 1 day and 15 years of age, including midline sagittal sections, were included. Children with a clinical history or MR imaging abnormalities that may affect the posterior fossa were excluded. We manually measured four 2D parameters: vermian height, anterior-posterior diameter of the vermis, anterior-posterior diameter of the midbrain-pons junction, and anterior-posterior midpons diameter. The inter- and intraobserver agreement was evaluated.

RESULTS

Seven hundred eighteen children were included (372 boys and 346 girls), from 1 day to 15 years of age. Normal values (third to 97th percentiles) were provided for each parameter. The vermis parameters showed a rapid growth phase during the first year, a slower growth until the fifth year, and finally a near-plateau phase. The brain stem parameters showed more progressive growth. The intra- and interobserver agreement was excellent for all parameters.

CONCLUSIONS

We provide reference biometric data of the vermis and the brain stem using simple and reproducible measurements that are easy to use in daily practice. The relevance of these 2D measurements should be further validated in diseases associated with cerebellar abnormalities.

The emerging role of Twist proteins in hematopoietic cells and hematological malignancies

Twist1 and Twist2 (Twist1–2) are two transcription factors, members of the basic helix-loop-helix family, that have been well established as master transcriptional regulators of embryogenesis and developmental programs of mesenchymal cell lineages. Their role in oncogenesis in epithelium-derived cancer and in epithelial-to-mesenchymal transition has also been thoroughly characterized. Recently, emerging evidence also suggests a key role for Twist1–2 in the function and development of hematopoietic cells, as well as in survival and development of numerous hematological malignancies. In this review, we summarize the latest data that depict the role of Twist1–2 in monocytes, T cells and B lymphocyte activation, and in associated hematological malignancies.

[Characteristics of tuberous sclerosis in children]

Tuberous sclerosis complex is a genetic multisystem disease characterized by hamartic development of many organs, most notably the brain, heart, kidneys, lungs, and skin. This autosomic dominant disorder results from mutations in one of two genes, TSC1 and TSC2, coding for hamartin and tuberin, respectively. The hamartin-tuberin complex inhibits the mammalian target of rapamycin pathway, which controls cell growth and proliferation. The clinical presentation is highly variable and most features of tuberous sclerosis become evident only in childhood after the child is several years of age, limiting their usefulness for early diagnosis. The aim of this article is to define the pediatric clinical manifestations of tuberous sclerosis in correlation with patient age. Sometimes, a prenatal diagnosis can be made based on fetal ultrasound and MRI, which show cardiac and brain lesions. However, newborns are most often asymptomatic. In the 1st year, seizures are the most common symptoms, with a high incidence of infantile spasms. In children between 2 and 10 years of age, neurological symptoms are the most frequent with epilepsy, mental retardation, and autism, but extraneurological manifestations can be diagnosed. In adolescents, most features of tuberous sclerosis become evident and renal and pulmonary manifestations must be sought. The knowledge of age-dependent clinical features of tuberous sclerosis can provide an earlier diagnosis and improve the management of these patients with a special role for multidisciplinary consultation.

[Antiepileptic drugs in pediatric migraine]

According to the criteria of the International Headache Society, migraine occurs in approximately 5 to 10% of children. As many as 30% of young patients with migraine experience such frequent and disabling attacks, or have unsatisfactory results and/or experience adverse effects with pharmacologic treatment of acute migraine attack, that daily preventive medications are required. Many studies have investigated the use of antiepileptic drugs in this indication but there is a paucity of placebo-controlled studies. So far, in the setting of migraine with and without aura, only flunarizine and topiramate have proved their efficacy in more than one placebo-controlled study. Uncontrolled studies suggest the possible efficacy of valproic acid, gabapentin, levetiracetam, zonisamide, and magnesium in preventive therapy of childhood periodic syndromes. Most of antiepileptic drugs used in pediatric preventive therapy are well tolerated. The most common adverse events are asthenia and somnolence.