Phenotype and molecular characterization of Wilson's disease in Morocco

BACKGROUND AND STUDY AIMS

In Morocco the prevalence of Wilson disease (WD) and the spectrum of mutations are not known. The aim of the present study was to estimate the prevalence of WD in Morocco, to evaluate the phenotype among a large cohort of WD patients, and to characterize ATP7B variants in a subgroup of WD patients.

PATIENTS AND METHODS

We collected data from 226 patients admitted to five university hospital centers in Morocco between 2008 and 2020. The diagnosis was based on clinical manifestations, function tests and biochemical parameters. The genotype was characterized in 18 families diagnosed at the University Hospital Center of Marrakesh, by next generation sequencing.

RESULTS

The mean annual prevalence in Morocco was 3.88 per 100,000 and the allele frequency was 0.15 %. Among the 226 patients included (121 males and 105 females), 196 were referred for a hepatic or neurological involvement and 30 were asymptomatic. The mean age at diagnosis was 13 ± 5.1 years (range: 5 - 42 years). Consanguinity was found in 63.3 % of patients. The mean duration of illness was 2.8 ± 1.9 years. Kayser-Fleischer rings were found in 131 (67.9 %) of 193 patients. Among the 196 symptomatic patients, 141/159 (88.7 %) had low serum ceruloplasmin (<0.2 g/L) and a high 24-hours urinary copper (>100 μg/day) was found in 173/182 (95.1 %) patients. The initial treatment was D-penicillamine in 207 patients, zinc acetate in five, zinc sulfate in five, and nine patients were not treated; 60/207 (29 %) patients have stopped treatment. A total of 72 patients died; the mortality rate was 31.9 %. Eight different ATP7B variants were identified among the 18 patients studied, of which two were novel (p.Cys1104Arg and p.Gln1277Hisfs*52), and six previously published (p.Gln289Ter, p.Cys305Ter, p.Thr1232Pro, p.Lys1020Arg, p.Glu583ArgfsTer25 and c.51+4A>T). All informative patients were homozygous for the disease-causing mutation.

CONCLUSION

In Morocco, a high prevalence due to consanguinity and a high mortality rate due to the difficulty of diagnosis and lack of treatment were observed in WD patients. NGS sequencing identified new ATP7B variants in WD patients from Morocco.

[Williams-Beuren syndrome: a retrospective study of a series of 11 cases at the Mohammed VI University Hospital in Marrakech]

Williams-Beuren syndrome is a rare genetic disease (1/20 000) characterized by a microdeletion at 7q11.23 encompassing about 28 genes, including the elastin gene, ELN. It is a sporadic disease in the majority of cases. Easily identifiable in childhood, this developmental disorder associates suggestive face dysmorphism, cardiac defect, psychomotor retardation and specific behavioural and cognitive profile. We conducted a retrospective study of 11 patients with Williams-Beuren syndrome whose data were collected in the Genetics Department of the Mohammed VI University Hospital of Marrakech. The average age of patients was 6.05 years (SD=6.56; interquartile range=5), with a female predominance (64%; 7/11 patients). Almost all patients were mentally retarded and the diagnosis was confirmed in 100% (11) of patients using fluorescence in situ hybridisation (FISH).

Clinical, biochemical and molecular characterization of Wilson's disease in Moroccan patients

Background

Wilson Disease (WD) is an autosomal recessive inherited metabolic disease caused by mutations in the ATP7B gene. WD is characterized by heterogeneous clinical presentations expressed by hepatic and neuropsychiatric phenotypes. The disease is difficult to diagnose, and misdiagnosed cases are commonly seen.

Methods

In this study, the presented symptoms of WD, the biochemical parameters as well as its natural history are described based on cases collected in Mohammed VI Hospital University of Marrakech (Morocco). We screened and sequenced 21 exons of ATP7B gene from 12 WD patients that confirmed through biochemical diagnosis.

Results

Mutational assessment of the ATP7B gene showed six homozygous mutations in 12 individuals however, 2 patients had no evidence of any mutation in promoter and exonic regions. All mutations are pathogenic and most were missense mutations. c.2507G > A (p.G836E), c.3694A > C (p.T1232P) and c.3310 T > C (p.C1104R) that were identified in 4 patients. The other mutations were a non-sense mutation (c.865C > T (p.C1104R)) detected in 2 patients, a splice mutation (c.51 + 4A > T) detected in 2 patients and a frameshift mutation (c.1746 dup (p.E583Rfs*25) detected in 2 patients.

Conclusion

Our study is the first molecular analysis in Moroccan patients with Wilson's disease, the ATP7B mutational spectrum in the Moroccan population is diverse and still unexplored.

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.

Spinocerebellar ataxia Type 7: clinical and genetic study of a new Moroccan family (case report)

Spinocerebellar ataxia type 7 (SCA7) is a rare autosomal dominant neurodegenerative disease. Its clinical presentation is a progressive cerebellar ataxia associated with cone and retinal dystrophy. The CAG repeat expansion in the ataxin-7 gene (ATXN7) causes spinocerebellar ataxia type 7 - a mutation that results in the degeneration of the brain stem cells, retina and cerebellum. We report in this study the clinical and genetic features of a new Moroccan family of SCA7, from the South of Morocco. We performed the molecular genetic testing to confirm the diagnosis of SCA7. The objective of this study is to report a new Moroccan case of SCA7 and to illustrate the role of the geneticist in the diagnosis, management and development of genetic counseling of SCA7 disease.

Union makes strength: a worldwide collaborative genetic and clinical study to provide a comprehensive survey of RD3 mutations and delineate the associated phenotype

Leber congenital amaurosis (LCA) is the earliest and most severe retinal degeneration (RD), and the most common cause of incurable blindness diagnosed in children. It is occasionally the presenting symptom of multisystemic ciliopathies which diagnosis will require a specific care of patients. Nineteen LCA genes are currently identified and three of them account for both non-syndromic and syndromic forms of the disease. RD3 (LCA12) was implicated as a LCA gene based on the identification of homozygous truncating mutations in two LCA families despite the screening of large cohorts of patients. Here we provide a comprehensive survey of RD3 mutations and of their clinical expression through the screening of a cohort of 852 patients originating worldwide affected with LCA or early-onset and severe RD. We identified three RD3 mutations in seven unrelated consanguineous LCA families - i.e., a 2 bp deletion and two nonsense mutations – predicted to cause complete loss of function. Five families originating from the Southern Shores of the Mediterranean segregated a similar mutation (c.112C>T, p.R38*) suggesting that this change may have resulted from an ancient founder effect. Considering the low frequency of RD3 carriers, the recurrence risk for LCA in non-consanguineous unions is negligible for both heterozygote and homozygote RD3 individuals. The LCA12 phenotype in our patients is highly similar to those of patients with mutant photoreceptor-specific guanylate cyclase (GUCY2D/LCA1). This observation is consistent with the report of the role of RD3 in trafficking of GUCYs and gives further support to a common mechanism of photoreceptor degeneration in LCA12 and LCA1, i.e., inability to increase cytoplasmic cGMP concentration in outer segments and thus to recover the dark-state. Similar to LCA1, LCA12 patients have no extraocular symptoms despite complete inactivation of both RD3 alleles, supporting the view that extraocular investigations in LCA infants with RD3 mutations should be avoided.

Genetic testing and first presymptomatic diagnosis in Moroccan families at high risk for breast/ovarian cancer

Germline mutations in the BRCA1 and BRCA2 genes highly predispose to breast and ovarian cancers and are responsible for a substantial proportion of familial breast and ovarian cancers. No female individuals from families from Morocco affected by breast cancer with mutations of these genes have previously been reported, and clinicians in Morocco are unaccustomed to dealing with healthy female individuals carrying mutations in the BRCA genes. This study aimed to report the initial experience of a group of Moroccan investigators carrying out predictive genetic testing to detect a known familial mutation in healthy Moroccan females with a high risk of developing breast cancer and to introduce supervision of these asymptomatic female carriers as a new approach in the prevention and early diagnosis of breast and ovarian cancers in Morocco. Presymptomatic diagnosis was carried out using DNA genetic testing in 5 healthy Moroccan female individuals from three families with an elevated risk of developing breast cancer. These are the first Moroccan families reported to be affected by breast cancers associated with BRCA mutations. Presymptomatic diagnosis was carried out for breast cancer in 5 female individuals from three Moroccan families with BRCA mutations. Two of the families are the first reported incidence of the founder mutation Ashkenazi BRCA1-185_186delAG in Moroccan patients. The third family carried the known BRCA2 mutation c.5073dupA/p.trp1692metfsX3. We tested the presence of these mutations in 5 asymptomatic healthy females from the three families. Two sisters from family 1 carried the BRCA1-185_186delAG mutation, whereas the third female individual from family 2 carried the c.5073dupA/p.trp1692metfsX3 mutation. However, one healthy female individual and her mother from family 3 did not carry the familial mutation of the BRCA1 gene. This study found BRCA mutations in three asymptomatic subjects, suggesting that this is the first step towards the development of persistent medical monitoring of females from families with a history of breast and ovarian cancers. Consequently, it is crucial for oncologists in Morocco to initiate the supervision of healthy female individuals with genetic defects which may lead to hereditary cancers.

[First North African observation of Leber congenital amaurosis secondary to CEP290 gene mutation]

Leber congenital amaurosis (LCA) is a the earliest and most severe form of retinal dystrophy responsible for congenital blindness. LCA has genetic heterogeneity and the study of this disease is elucidating the genetics and molecular interactions involved in the development of the retina. To date, 11 LCA genes have been mapped, ten of which have been identified. The CEP290 gene has been shown to account for Joubert and Senior-Loken syndromes and to be a frequent cause of nonsyndromic LCA. We report here the first Arab patient, born to consanguineous parents, with Leber congenital amaurosis attributable to mutation of the CEP290 gene.

[The mutation 35delG of the gene of the connexin 26 is a frequent cause of autosomal-recessive non-syndromic hearing loss in Morocco]

Mutations of the connexin 26 gene, GJB2, are the most common cause of non syndromic autosomal-recessive hearing loss. One of the GJB2 mutations, the 35delG, is recurrent in European and Mediterranean populations with allelic frequency of at least 70% in patients with hearing loss caused by GJB2 impairment.

OBJECTIVES

To determine the prevalence of the 35delG mutation in non-syndromic autosomal-recessive deafness in Morocco.

PATIENTS AND METHODS

We looked for the 35delG mutation among 25 non-related Moroccan children suffering from an autosomal recessive hearing loss. A screening for GJB2 mutations, and then a search for GJB6 deletions were carried out among patients who do not bear the 35delG.

RESULTS

Twelve patients were homozygous for the 35delG mutation. This mutation was responsible for almost half of the hearing loss among our patients (48%). There was no other GJB2 or GJB6 mutation among 13 patients.

CONCLUSION

This study underlines the advantages of a systematic search for this mutation among deaf children when environmental causes are considered irrelevant. The identification of this genetic anomaly signs the etiologic diagnosis of deafness, which allows a relevant genetic advice, and a better treatment of patients.