Patchy white matter hyperintensity in ring chromosome 18 syndrome

Imaging Findings and MRI Patterns in a Cohort of 18q Chromosomal Abnormalities

BACKGROUND AND PURPOSE

The abnormalities of the long arm of chromosome 18 (18q) constitute a complex spectrum. We aimed to systematically analyze their MR imaging features. We hypothesized that there would be variable but recognizable white matter and structural patterns in this cohort.

MATERIALS AND METHODS

In this retrospective cohort study, we included pediatric patients with a proved abnormality of 18q between 2000-2022. An age- and sex-matched control cohort was also constructed.

RESULTS

Thirty-six cases, median MR imaging age 19.6 months (4.3-59.3), satisfied our inclusion criteria. Most were female (25, 69%, F:M ratio 2.2:1). Fifty MR imaging studies were analyzed, and 35 (70%) had delayed myelination. Two independent readers scored brain myelination with excellent interrater reliability. Three recognizable evolving MR imaging patterns with distinct age distributions and improving myelination scores were identified: Pelizaeus-Merzbacher disease-like (9.9 months, 37), intermediate (22 months, 48), and washed-out pattern (113.6 months, 53). Etiologically, MRIs were analyzed across 3 subgroups: 18q deletion (34, 69%), trisomy 18 (10, 21%), and ring chromosome 18 (5, 10%). Ring chromosome 18 had the highest myelination lag (27, P = .005) and multifocal white matter changes (P = .001). Trisomy 18 had smaller pons and cerebellar dimensions (anteposterior diameter pons, P = .002; corpus callosum vermis, P < .001; and transverse cerebellar diameter, P = .04).

CONCLUSIONS

In this cohort of 18q chromosomal abnormalities, MR imaging revealed recognizable patterns correlating with improving brain myelination. Imaging findings appear to be on a continuum with more severe white matter abnormalities in ring chromosome 18 and greater prevalence of structural abnormalities of the pons and cerebellum in trisomy 18.

Mosaic ring chromosome 18 in a Chinese child with epilepsy: a case report and review of the literature

BACKGROUND

Ring chromosome 18 (r[18]) is a rare syndrome in which one or both ends of chromosome 18 are lost and the remaining chromosome rejoins to form ring-shaped figures. It is characterized by developmental delay/cognitive disability, facial dysmorphisms, and immunological problems. The phenotype associated with epilepsy is rare and has not yet been reported in China.

METHODS

We report herein the case of a 12-year-old Chinese girl who presented with typical facial dysmorphisms, developmental delay, cognitive disability, hyperactivity, and epilepsy and discuss the clinical features of r(18) syndromes through comparison with previously described cases worldwide.

RESULTS

We describe the characteristics of all seizures that have been reported in these cases and propose that the appearance of epilepsy in r(18) patients may be associated with the abnormality of chromosome karyotypes. Further studies are warranted to confirm this.

Genetic disorders with central nervous system white matter abnormalities: An update

Several genetic disorders have variable degree of central nervous system white matter abnormalities. We retrieved and reviewed 422 genetic conditions with prominent and consistent involvement of white matter from the literature. We herein describe the current definitions, classification systems, clinical spectrum, neuroimaging findings, genomics, and molecular mechanisms of these conditions. Though diagnosis for most of these disorders relies mainly on genomic tests, specifically exome sequencing, we collate several clinical and neuroimaging findings still relevant in diagnosis of clinically recognizable disorders. We also review the current understanding of pathophysiology and therapeutics of these disorders.

A Case of Ring Chromosome 18 with Single Umbilical Artery Detected During Prenatal Period

Fetuses with a single umbilical artery have a risk of increased chromosomal anomalies and congenital malformations. Ring chromosomes are rare and the phenotypic and clinical characteristics of affected individuals show great variability depending on the quantity of the lost critical genes or gains during the formation of the ring or due to mitotic instability. Ring chromosome 18 [r(18)] is characterized by short stature, craniofacial dysmorphism, mental and motor retardation, autoimmune disorders, extremity anomalies, dermal lesions, structural heart malformations, and kidney abnormalities. In this study, the clinical findings of a female patient who had a single umbilical artery in the prenatal period and was diagnosed as de novo r(18) by molecular karyotype analysis were compared with those in the literature. A detailed ultrasonographic examination of the fetus with a single umbilical artery may enable the detection of additional anomalies and thus the early diagnosis of chromosomal anomalies may be possible with prenatal genetic analysis.

Central and peripheral dysmyelination in a 3-year-old girl with ring chromosome 18

Myelin basic protein (MBP) contributes to peripheral and central nervous system myelin. Developmental myelinopathies exist on a clinical spectrum, but MBP is not included on leukodystrophy or CMT gene panels. This ring chromosome 18 case presents serial MRI and EMG/NCS, shedding light on the early clinical course of the disorder.