Monosomy 1p36 - a multifaceted and still enigmatic syndrome: four clinically diverse cases with shared white matter abnormalities

The Spectrum of the Prader-Willi-like Pheno- and Genotype: A Review of the Literature

Prader-Willi syndrome (PWS) is a rare genetic syndrome, caused by the loss of expression of the paternal chromosome 15q11-q13 region. Over the past years, many cases of patients with characteristics similar to PWS, but without a typical genetic aberration of the 15q11-q13 region, have been described. These patients are often labelled as Prader-Willi-like (PWL). PWL is an as-yet poorly defined syndrome, potentially affecting a significant number of children and adults. In the current clinical practice, patients labelled as PWL are mostly left without treatment options. Considering the similarities with PWS, children with PWL might benefit from the same care and treatment as children with PWS. This review gives more insight into the pheno- and genotype of PWL and includes 86 papers, containing 368 cases of patients with a PWL phenotype. We describe mutations and aberrations for consideration when suspicion of PWS remains after negative testing. The most common genetic diagnoses were Temple syndrome (formerly known as maternal uniparental disomy 14), Schaaf-Yang syndrome (truncating mutation in the MAGEL2 gene), 1p36 deletion, 2p deletion, 6q deletion, 6q duplication, 15q deletion, 15q duplication, 19p deletion, fragile X syndrome, and Xq duplication. We found that the most prevalent symptoms in the entire group were developmental delay/intellectual disability (76%), speech problems (64%), overweight/obesity (57%), hypotonia (56%), and psychobehavioral problems (53%). In addition, we propose a diagnostic approach to patients with a PWL phenotype for (pediatric) endocrinologists. PWL comprises a complex and diverse group of patients, which calls for multidisciplinary care with an individualized approach.

1p36 deletion syndrome: first case report in Morocco detected by fluorescence in situ hybridization

The 1p36 deletion syndrome results from a heterozygous deletion of the terminal chromosomal band of the short arm of chromosome 1. Monosomy 1p36 is the most common terminal deletion observed in men (1 in 5000 newborns), characterized by distinctive dysmorphia, delayed growth, psychomotor retardation, intellectual deficit, epilepsy and heart defects. Fluorescence in situ hybridization (FISH) and comparative genomic hybridization (CGH-array) are currently the two best diagnostic techniques. The objective of this work is to take stock of the first Moroccan case of 1p36 deletion and to illustrate the role of the geneticist in the diagnosis and management of this syndrome. There is currently no effective medical treatment for this disease.

Phenotypic and Molecular Cytogenetic Analysis of a Case of Monosomy 1p36 Syndrome due to Unbalanced Translocation

Monosomy 1p36 syndrome is one of the most common submicroscopic deletion syndromes, which is characterized by the presence of delayed developmental milestones, intellectual disability, and clinically recognizable dysmorphic craniofacial features. The syndrome comprises 4 cytogenetic groups including pure terminal deletions, interstitial deletions, complex rearrangements, and derivative chromosomes 1 due to unbalanced translocations, where unbalanced translocations represent the least percentage of all cases of monosomy 1p36 (7%). Most patients with monosomy 1p36 due to an unbalanced translocation can be cytogenetically diagnosed using conventional techniques. However, chromosomal microarray analysis is mandatory in these cases to detect copy number variance and size of the deletion and allows for setting a phenotype-genotype correlation. Here, we studied a 1.5-year-old female patient who showed intellectual disability, delayed milestones, hypotonia, seizures, and characteristic dysmorphic features including brachycephaly, straight eyebrows, deep-set eyes, downslanting palpebral fissures, midface hypoplasia, depressed nasal bridge, long philtrum, and pointed chin. Conventional cytogenetic analysis (CCA), microarray study, and fluorescence in situ hybridization (FISH) analysis were performed. CCA showed a translocation involving chromosomes 1 and 21, 45,XX,der(1)t(1;21)(p36.32;q21.1)dn. Microarray analysis revealed copy number losses at both 1p36 and proximal 21q. FISH confirmed the presence of the 1p36 deletion, but was not performed for 21q. We have concluded that phenotype-genotype correlation for monosomy 1p36 syndrome can be performed for the fundamental clinical manifestations; however, the final aspect of the syndrome depends on composite factors. Monosomy 1p36 due to unbalanced translocation may present either classically or with additional altered features of various severity based on the copy number variations involving different chromosomes.

Electroclinical features of epilepsy monosomy 1p36 syndrome and their implications

OBJECTIVIES

Monosomy 1p36 syndrome is a recognized syndrome with multiple congenital anomalies; medical problems of this syndrome include developmental delay, facial dysmorphisms, hearing loss, short stature, brain anomalies, congenital heart defects. Epilepsy can be another feature but there are few data about the types of seizures and long term prognosis. The aim of this work was to analyse the electroclinical phenotype and the long-term outcome in patients with monosomy 1p36 syndrome and epilepsy.

MATERIALS AND METHODS

Data of 22 patients with monosomy 1p36 syndrome and epilepsy were reconstructed by reviewing medical records. For each patient we analysed age at time of diagnosis, first signs of the syndrome, age at seizure onset, seizure type and its frequency, EEG and neuroimaging findings, the response to antiepileptic drugs treatment and clinical outcome up to the last follow-up assessment.

RESULTS

Infantile Spasm (IS) represents the most frequent type at epilepsy onset, which occurs in 36.4% of children, and a half of these were associated with hypsarrhythmic electroencephalogram. All patients with IS had persistence of seizures, unlike other patients with different seizures onset. Children with abnormal brain neuroimaging have a greater chance to develop pharmacoresistant epilepsy.

CONCLUSION

This syndrome represents a significant cause of IS: these patients, who develop IS, can suffer from pharmacoresistent epilepsy, that is more frequent in children with brain abnormalities.

Electroclinical features of epilepsy associated with 1p36 deletion syndrome: A review

1p36 terminal deletion is a recently recognized syndrome with multiple congenital anomalies and intellectual disability. It occurs approximately in 1 out of 5000 to 10,000 live births and is the most common subtelomeric microdeletion observed in human. Medical problems commonly caused by terminal deletions of 1p36 include developmental delay, intellectual disability, seizures, vision problems, hearing loss, short stature, brain anomalies, congenital heart defects, cardiomyopathy, renal anomalies and distinctive facial features. Although the syndrome is considered clinically recognizable, there is significant phenotypic variation among affected individuals. Genotype-phenotype correlation in this syndrome is complicated, because of the similar clinical evidence seen in patients with different deletion sizes. We review 34 scientific articles from 1996 to 2016 that described 315 patients with 1p36 delection syndrome. The aim of this review is to find a correlation between size of the 1p36-deleted segments and the neurological clinical phenotypes with the analysis of electro-clinical patterns associated with chromosomal aberrations, that is a major tool in the identification of epilepsy susceptibility genes. Our finding suggest that developmental delay and early epilepsy are frequent findings in 1p36 deletion syndrome that can contribute to a poor clinical outcome for this reason this syndrome should be searched for in patients presenting with infantile spasms associated with a hypsarrhythmic EEG, particulary if they are combined with dismorphic features, severe hypotonia and developmental delay.