Novel Mutations in Two Saudi Patients with Congenital Retinal Dystrophy

Alström Syndrome: A Challenging Case Study of a Female Saudi Patient With Type 2 Diabetes Mellitus and Complete Vision Loss

Alström syndrome is a genetic disease that impacts numerous systems in the human body. The symptoms can vary and appear gradually. Childhood obesity, heart disease (cardiomyopathy), abnormalities in vision, and hearing issues are the main symptoms of this disorder in children. Diabetes mellitus, hepatic issues, and renal dysfunction can all occur over time. Genetic alterations in the ALMS1 gene are the cause of Alström syndrome. It has an autosomal recessive inheritance pattern. We address the case of a Saudi woman in her 20s. She had been initially referred for type 2 diabetes, intellectual disability since early childhood, metabolic acidosis, and micrognathia; however, she also exhibited blindness, chronic kidney disease (CKD), and hearing loss, all of which are indicative of Alström syndrome. DNA testing showed that she has a homozygous pathogenic variant in the ALMS gene. Autosomal recessive Alström syndrome has been confirmed as a genetic diagnosis. No other clinically significant variations were found that are associated with the mentioned phenotype. By reporting this mutation, we hope to learn more about the genotypic range of the disease, particularly in the Saudi population. As each member of the family underwent genetic testing, we established a stringent follow-up schedule for our patient and her family.

Alstrom's Syndrome: An Experience of Tertiary Care Center

Alstrom's syndrome (AS) is an autosomal recessively inherited multisystemic disorder that falls under the umbrella of ciliopathy. It is characterized by poor vision, hearing impairment, cardiomyopathy, childhood obesity, diabetes mellitus type 2, dyslipidemia, pulmonary, hepatic, and renal failure besides systemic fibrosis. Biallelic pathogenic variants in ALMS1 gene cause AS. Retrospective study (1990–2017) included 12 Saudi patients with AS based on their phenotype, biochemical markers, and genotype. The study was approved by Fisal Specialist Hospital and Research Centre, Riyadh (RAC number 2131129) on October 2, 2012. This study showed clinical and genetic heterogeneity; six patients showed a founder mutation (IVS18–2A > T in exon 19), whereas six others showed private mutations. AS in Saudi Arabia is underdiagnosed probably because of its variable clinical manifestations. We report 12 Saudi patients with AS to enhance the awareness about this syndrome.

Identification of a Rare Exon 19 Skipping Mutation in ALMS1 Gene in Alström Syndrome Patients From Two Unrelated Saudi Families

Background: Alström syndrome (AS) is a very rare childhood disorder characterized by cardiomyopathy, progressive hearing loss and blindness. Inherited genetic variants of ALMS1 gene are the known molecular cause of this disease. The objective of this study was to characterize the genetic basis and understand the genotype-phenotype relationship in Saudi AS patients. Methods: Clinical phenotyping and whole-exome sequencing (WES) analysis were performed on six AS patients belonging to two unrelated consanguineous Saudi families. Sanger sequencing was performed to determine the mode of inheritance of ALMS1 variant in first-degree family relatives and also to ensure its rare prevalence in 100 healthy population controls. Results: We identified that Alström patients from both the families were sharing a very rare ALMS1, 3'-splice site acceptor (c.11873-2 A>T) variant, which skips entire exon-19 and shortens the protein by 80 amino acids. This disease variant was inherited by AS patients in autosomal recessive mode and is not yet reported in any population-specific genetic databases. AS patients carrying this mutation showed heterogeneity in clinical presentations. Computational analysis of the mutant centroid structure of ALMS1 mRNA revealed that exon-19 skipping enlarges the hairpin loop and decreases the free energy, eventually affecting its folding pattern, stability, and function. Hence, we propose c.11873-2A as an AS causative potential founder mutation in Saudi Arabia because it is found in two families lacking a common lineage. Conclusions: We conclude that WES analysis potentially helps in clinical phenotyping, early diagnosis, and better clinical management of Alström patients showing variable clinical expressivity.

Whole exome sequencing identifies rare biallelic ALMS1 missense and stop gain mutations in familial Alström syndrome patients

Alström syndrome (AS, OMIM ID 203800) is a rare childhood multiorgan disorder, which is widely studied in non-Arab ethnic patients. The clinical and molecular basis of AS and the mode of disease inheritance in consanguineous Arab populations is not well investigated. Therefore, to identify the molecular basis of AS in familial forms, the present study performed whole exome sequencing of 5 AS patients belonging to 2 different Bedouin families from Saudi Arabia. The present study identified the AS causative rare biallelic mutations in ALMS gene:T376S in exon 5 and S909* in exon 8 for family A and an R2721* in exon 10 (R2721*) for family B. ALMS1 targeted genetic sequencing of healthy population controls and family members has confirmed its extremely rare frequency and autosomal recessive mode of inheritance. The truncating mutations S909* and R2721* could cause the loss of CC domains and ALMS motif on C-terminal end of the protein and creates unstable protein, which eventually undergoes intracellular degradation. The premature protein truncating mutations described in our study may eventually provide further insight into the functional domains of the ALMS1 protein and contribute to the understanding of the phenotypic spectrum of AS. Whole exome sequencing based molecular diagnosis is expected to rule out ambiguity surrounding clinical diagnosis of suspected AS cases.

Alström syndrome: A novel mutation in Saudi girl with insulin-resistant diabetes

RATIONALE

Alström syndrome is an autosomal recessive disorder characterized by hearing loss, blindness, obesity, non-insulin dependent diabetes, and others.

PATIENT CONCERN

A 10 years old Saudi girl, who presented with diabetic ketoacidosis and found to have hearing loss and blindness.

DIAGNOSIS

Alström syndrome.

INTERVENTIONS

Multidisciplinary team approach, with echocardiography, hearing test, eye exam and genetic test for Alström syndrome.

OUTCOMES

The patient has retinitis pigmentosa, bilateral hearing loss, double diabetes with weakly positive anti-insulin antibodies and DNA analysis showed novel mutation for Alström syndrome.

LESSONS

the combination of obesity, diabetes, hearing loss and blindness should alert the physician to test for Alström syndrome.