Respiratory manifestations in 38 patients with Alström syndrome

Alström syndrome-wide clinical variability within the same variant: a case report and literature review

Background

Alström disease is a rare disorder caused by various variants in the ALMS1 gene. It is characterised by multiorgan involvement, namely neurosensory deficits, endocrine and metabolic disturbances, cardiomyopathy, and hepatic and renal dysfunction. The disease exhibits marked interindividual variability, both in clinical manifestations and age of onset. Several attempts have been made to establish a relationship between phenotype and genotype, with little success.

Methods

We present the case of an infant who presented with dilated cardiomyopathy, above-average weight and neurosensory deficits, raising the suspicion for Alström syndrome, later confirmed through genetic testing. Moreover, we conducted an extensive literature search to identify all reported cases having the same variant as our patient, in order to evaluate whether specific mutated alleles have a role in determining phenotype-genotype associations.

Results

A 4-month-old female infant with a recent history of bronchiolitis was referred to our centre due to a systolic murmur. In our service, the clinical exam was significant for above-average weight, dyspnea, wheezing and a grade II systolic murmur. Echocardiography revealed dilated cardiomyopathy with severe systolic dysfunction of the left ventricle. Laboratory investigations revealed elevated NT-proBNP and troponin levels, along with positive IgM antibodies for CMV and EBV. Dilated cardiomyopathy attributed to viral myocarditis was suspected. Treatment with ACE inhibitors and diuretics was started, with a favourable response initially. However, after a few months, the patient presented with vertical nystagmus and head bobbing. The ophthalmologic exam revealed cone-rode dystrophy. Considering the constellation of symptoms, Alström syndrome was suspected. Genetic testing revealed a homozygous variant [c.4156dup (p.Thr1386Asnfs*15)] in the ALMS1 gene, confirming the diagnosis.

Conclusion

Our literature review revealed 8 additional cases harbouring the same variant as our patient, five in a heterozygous state, two in a homozygous state and one with only one allele identified. The identified patients presented high heterogeneity of clinical manifestations and age of onset. The heterogeneity persisted even in patients with homozygous variants, suggesting the involvement of factors beyond the specific disease-causing variant in determining disease manifestation. Therefore, genotype-phenotype correlations might not be supported by specific variants.

Alström Syndrome: A Review Focusing on Its Diverse Clinical Manifestations and Their Etiology as a Ciliopathy

Alström syndrome is a form of inherited obesity caused by a single gene abnormality and is inherited as an autosomal recessive trait. It is characterised by a variety of clinical manifestations, including progressive visual and hearing impairment, type 2 diabetes mellitus, dilated cardiomyopathy, and hepatic and renal dysfunction, in addition to obesity. Recent insights underline the pivotal involvement of the disease-associated gene (ALMS1) in cilia formation and function, leading to the classification of its clinical manifestations as a ciliopathy. This review delineates the diverse clinical indicators defining the syndrome and elucidates its pathological underpinnings.

Genotype-phenotype associations in Alström syndrome: a systematic review and meta-analysis

BACKGROUND

Alström syndrome (ALMS; #203800) is an ultrarare monogenic recessive disease. This syndrome is associated with variants in the ALMS1 gene, which encodes a centrosome-associated protein involved in the regulation of several ciliary and extraciliary processes, such as centrosome cohesion, apoptosis, cell cycle control and receptor trafficking. The type of variant associated with ALMS is mostly complete loss-of-function variants (97%) and they are mainly located in exons 8, 10 and 16 of the gene. Other studies in the literature have tried to establish a genotype-phenotype correlation in this syndrome with limited success. The difficulty in recruiting a large cohort in rare diseases is the main barrier to conducting this type of study.

METHODS

In this study we collected all cases of ALMS published to date. We created a database of patients who had a genetic diagnosis and an individualised clinical history. Lastly, we attempted to establish a genotype-phenotype correlation using the truncation site of the patient's longest allele as a grouping criteria.

RESULTS

We collected a total of 357 patients, of whom 227 had complete clinical information, complete genetic diagnosis and meta-information on sex and age. We have seen that there are five variants with high frequency, with p.(Arg2722Ter) being the most common variant, with 28 alleles. No gender differences in disease progression were detected. Finally, truncating variants in exon 10 seem to be correlated with a higher prevalence of liver disorders in patients with ALMS.

CONCLUSION

Pathogenic variants in exon 10 of the ALMS1 gene were associated with a higher prevalence of liver disease. However, the location of the variant in the ALMS1 gene does not have a major impact on the phenotype developed by the patient.

Supportive care in a patient with Alstrom syndrome with hyperphenylalaninemia and sleep problems

Alstrom syndrome is a rare genetic disorder with an autosomal recessive mutation in the ALMS1 gene. The disease's manifestations include ophthalmic problems, hearing loss, obesity, and cardiovascular disorders. In addition, medical cases include other organ complications. However, the overlapping variety of such symptoms with other diseases may delay the diagnosis. In this article, we describe the case of a 7-year-old female patient with Alstrom syndrome, and cardiovascular and hyperphenylalaninemia diseases since birth. Other symptoms included diabetes and ophthalmologic problems with skeletal disability. Blindness and hearing impairment were diagnosed, along with recurrence of respiratory problems at the age of 7 years. The patient's obesity-induced snoring predisposed her to uncontrolled blood glucose. In fact, respiratory tract problems and sleep disorders had occurred as a degraded cycle and left her with a severe disability for years. The similarity of the symptoms with other diseases had misled the physician in diagnosis. However, a polysomnography test (because of complaints of short sleep duration) recognized the source of the patient's sleep disorders and breathing problems. Eventually, we delivered a portable ventilator to the child for continuous positive airway pressure (CPAP) therapy. The child's breathing and oxygenation conditions improved. Using the ventilator and the CPAP system, we discharged her from the hospital without requiring oxygenation, in a stable condition. The procedure could prevent the patient from hypoxia and retinal problem.

Hematopoietic Stem Cells and Metabolic Deterioration in Alström Syndrome, a Rare Genetic Model of the Metabolic Syndrome

Alström syndrome (AS) is a rare genetic disease caused by ALMS1 mutations, characterized by short stature, and vision and hearing loss. Patients with AS develop the metabolic syndrome, long-term organ complications, and die prematurely. We explored the association between AS and a shortage of hematopoietic stem/progenitor cells (HSPCs), which is linked to metabolic diseases and predicts diabetic complications. We included patients with AS at a national referral center. We measured HSPCs with flow cytometry at baseline and follow-up. We followed patients up to January 2022 for metabolic worsening and end-organ damage. We evaluated HSPC levels and mobilization as well as bone marrow histology in a murine model of AS. In 23 patients with AS, we found significantly lower circulating HSPCs than in healthy blood donors (-40%; P = .002) and age/sex-matched patients (-25%; P = .022). Longitudinally, HSPCs significantly declined by a further 20% in patients with AS over a median of 36 months (interquartile range 30-44). Patients with AS who displayed metabolic deterioration over 5.3 years had lower levels of HSPCs, both at baseline and at last observation, than those who did not deteriorate. Alms1-mutated mice were obese and insulin resistant and displayed significantly reduced circulating HSPCs, despite no overt hematological abnormality. Contrary to what was observed in diabetic mice, HSPC mobilization and bone marrow structure were unaffected. We found depletion of HSPCs in patients with AS, which was recapitulated in Alms1-mutated mice. Larger and longer studies will be needed to establish HSPCs shortage as a driver of metabolic deterioration leading to end-organ damage in AS.

Hearing Loss in Adults With Alström Syndrome-Experience From the UK National Alström Service

OBJECTIVE

To characterize the patterns of hearing loss and methods of hearing rehabilitation in the UK national cohort of adults with Alström syndrome.

STUDY DESIGN

Retrospective review of electronic patient records.

SETTING

UK National multi-disciplinary team (MDT) Alström service held at the Queen Elizabeth Hospital, Birmingham.

PATIENTS

Forty one adult patients with a diagnosis of Alström syndrome, confirmed via ALMS1 gene sequencing, are under ongoing review within the UK National MDT Alström service.

MAIN OUTCOME MEASURES

Magnitude and type of hearing loss were analyzed using patients' audiometric data. Deterioration of hearing was calculated using serial pure tone audiograms. Methods of hearing rehabilitation used by patients and potential candidacy for cochlear implantation were analyzed.

RESULTS

Of 34 patients with available audiograms, all had sensorineural hearing loss (SNHL). Dual sensory (visual and hearing) loss was present in 32/34 (94%) patients. Hearing deteriorated with advancing age, at 1.23 dB/yr. Severe- profound SNHL was present in 9/34 (26%) cases. Air conduction hearing aids were used in 27/34 (79%) cases, and cochlear implants in 2/34 (5%).

CONCLUSIONS

Alström syndrome is an ultra-rare genetic disorder with progressive, debilitating multi-system manifestations, including SNHL. The UK National MDT Alström service represents one of the largest reported adult cohorts in the world. SNHL in this group was ubiquitous, showing a rapid decline in hearing with age. Annual audiometric assessment to enable early diagnosis of hearing loss and optimum rehabilitation are paramount to minimize the impact of hearing loss in this condition.

Nasal Nitric Oxide Measurement in Primary Ciliary Dyskinesia. A Technical Paper on Standardized Testing Protocols

Nasal nitric oxide concentrations are extremely low in primary ciliary dyskinesia (PCD), and measurement of this nasal gas is recommended as a PCD diagnostic test in cooperative patients aged 5 years and older. However, nasal nitric oxide measurements must be performed with chemiluminescence analyzers using a standardized protocol to ensure proper results, because nasal nitric oxide values can be influenced by various internal and external factors. Repeat nasal nitric oxide testing on separate visits is required to ensure that low diagnostic values are persistent and consistent with PCD. This technical paper presents the standard operating procedures for nasal nitric oxide measurement used by the PCD Foundation Clinical and Research Centers Network at various specialty centers across North America. Adherence to this document ensures reliable nasal nitric oxide testing and high diagnostic accuracy when employed in a population with appropriate clinical phenotypes for PCD.

Variant profiles of genes mapping to chromosome 16q loss in Wilms tumors reveals link to cilia-related genes and pathways

Background: Wilms tumor is the most common pediatric renal tumor and the fourth most common malignancy in children. Chromosome 16q deletion(del) or loss of heterozygosity (LOH) has been correlated with recurrence and overall poor prognosis, such that patients with 16qLOH and 1p allelic loss are treated with more aggressive chemotherapeutic regimens.

Methods: In the present study, we have compared the variant profiles of Wilms tumors with and without 16q del/LOH using both data available from the TARGET database (42 samples) and tumors procured from our legacy collection (8 samples). Exome-Seq data was analyzed for tumor specific variants mapping to 16q. Whole exome analysis was also performed. An unbiased approach for somatic variant analysis was used to detect tumor-specific, somatic variants.

Results: Of the 72 genes mapping to 16q, 42% were cilia-related genes and 28% of these were found to carry somatic variants specific to those tumors with 16qdel/LOH. Whole exome analyses further revealed that 30% of cilia-related genes across the genome carried alterations in tumors both with and without 16qdel/LOH. Additional pathway analyses revealed that many cilia-related pathway members also carried deleterious variant in these tumors including Sonic Hedgehog (SHh), Wnt, and Notch signaling pathways.

Conclusions: The data suggest that cilia-related genes and pathways are compromised in Wilms tumors. The genes on chromosome 16q that carry deleterious variants in cilia-related genes may account for the more aggressive nature of tumors with 16q del/LOH.

Consensus clinical management guidelines for Alström syndrome

Alström Syndrome (ALMS) is an ultra-rare multisystem genetic disorder caused by autosomal recessive variants in the ALMS1 gene, which is located on chromosome 2p13. ALMS is a multisystem, progressive disease characterised by visual disturbance, hearing impairment, cardiomyopathy, childhood obesity, extreme insulin resistance, accelerated non-alcoholic fatty liver disease (NAFLD), renal dysfunction, respiratory disease, endocrine and urologic disorders. Clinical symptoms first appear in infancy with great variability in age of onset and severity. ALMS has an estimated incidence of 1 case per 1,000,000 live births and ethnically or geographically isolated populations have a higher-than-average frequency. The rarity and complexity of the syndrome and the lack of expertise can lead to delayed diagnosis, misdiagnosis and inadequate care. Multidisciplinary and multiprofessional teams of experts are essential for the management of patients with ALMS, as early diagnosis and intervention can slow the progression of multi-organ dysfunctions and improve patient quality of life.These guidelines are intended to define standard of care for patients suspected or diagnosed with ALMS of any age. All information contained in this document has originated from a systematic review of the literature and the experiences of the authors in their care of patients with ALMS. The Appraisal of Guidelines for Research & Evaluation (AGREE II) system was adopted for the development of the guidelines and for defining the related levels of evidence and strengths of recommendations.These guidelines are addressed to: a) specialist centres, other hospital-based medical teams and staffs involved with the care of ALMS patients, b) family physicians and other primary caregivers and c) patients and their families.

Motile ciliopathies

Motile cilia are highly complex hair-like organelles of epithelial cells lining the surface of various organ systems. Genetic mutations (usually with autosomal recessive inheritance) that impair ciliary beating cause a variety of motile ciliopathies, a heterogeneous group of rare disorders. The pathogenetic mechanisms, clinical symptoms and severity of the disease depend on the specific affected genes and the tissues in which they are expressed. Defects in the ependymal cilia can result in hydrocephalus, defects in the cilia in the fallopian tubes or in sperm flagella can cause female and male subfertility, respectively, and malfunctional motile monocilia of the left-right organizer during early embryonic development can lead to laterality defects such as situs inversus and heterotaxy. If mucociliary clearance in the respiratory epithelium is severely impaired, the disorder is referred to as primary ciliary dyskinesia, the most common motile ciliopathy. No single test can confirm a diagnosis of motile ciliopathy, which is based on a combination of tests including nasal nitric oxide measurement, transmission electron microscopy, immunofluorescence and genetic analyses, and high-speed video microscopy. With the exception of azithromycin, there is no evidence-based treatment for primary ciliary dyskinesia; therapies aim at relieving symptoms and reducing the effects of reduced ciliary motility.

Clinical characteristics of individual organ system disease in non-motile ciliopathies

Non-motile ciliopathies (disorders of the primary cilia) include autosomal dominant and recessive polycystic kidney diseases, nephronophthisis, as well as multisystem disorders Joubert, Bardet-Biedl, Alström, Meckel-Gruber, oral-facial-digital syndromes, and Jeune chondrodysplasia and other skeletal ciliopathies. Chronic progressive disease of the kidneys, liver, and retina are common features in non-motile ciliopathies. Some ciliopathies also manifest neurological, skeletal, olfactory and auditory defects. Obesity and type 2 diabetes mellitus are characteristic features of Bardet-Biedl and Alström syndromes. Overlapping clinical features and molecular heterogeneity of these ciliopathies render their diagnoses challenging. In this review, we describe the clinical characteristics of individual organ disease for each ciliopathy and provide natural history data on kidney, liver, retinal disease progression and central nervous system function.

Pathophysiology, causes and genetics of paediatric and adult bronchiectasis

Bronchiectasis has historically been considered to be irreversible dilatation of the airways, but with modern imaging techniques it has been proposed that 'irreversible' be dropped from the definition. The upper limit of normal for the ratio of airway to arterial development increases with age, and a developmental perspective is essential. Bronchiectasis (and persistent bacterial bronchitis, PBB) is a descriptive term and not a diagnosis, and should be the start not the end of the patient's diagnostic journey. PBB, characterized by airway infection and neutrophilic inflammation but without significant airway dilatation may be a precursor of bronchiectasis, and there are many commonalities in the microbiology and the pathology, which are reviewed in this article. A high index of suspicion is essential, and a history of chronic wet or productive cough for more than 4-8 weeks should prompt investigation. There are numerous underlying causes of bronchiectasis, although in many cases no cause is found. Causes include post-infectious, especially after tuberculosis, adenoviral or pertussis infection; aspiration syndromes; defects in host defence, which may solely affect the airways (cystic fibrosis, not considered in this review, and primary ciliary dyskinesia); and primary ciliary dyskinesia or be systemic, such as common variable immunodeficiency; genetic syndromes; and anatomical defects such as intraluminal airway obstruction (e.g. foreign body), intramural obstruction (e.g. complete cartilage rings) and external airway compression (e.g. by tuberculous lymph nodes). Identification of the underlying cause is important, because some of these conditions have specific treatments and others genetic implications for the family.

ALMS1 and Alström syndrome: a recessive form of metabolic, neurosensory and cardiac deficits

Alström syndrome (AS) is characterised by metabolic deficits, retinal dystrophy, sensorineural hearing loss, dilated cardiomyopathy and multi-organ fibrosis. Elucidating the function of the mutated gene, ALMS1, is critical for the development of specific treatments and may uncover pathways relevant to a range of other disorders including common forms of obesity and type 2 diabetes. Interest in ALMS1 is heightened by the recent discovery of its involvement in neonatal cardiomyocyte cell cycle arrest, a process with potential relevance to regenerative medicine. ALMS1 encodes a ~ 0.5 megadalton protein that localises to the base of centrioles. Some studies have suggested a role for this protein in maintaining centriole-nucleated sensory organelles termed primary cilia, and AS is now considered to belong to the growing class of human genetic disorders linked to ciliary dysfunction (ciliopathies). However, mechanistic details are lacking, and recent studies have implicated ALMS1 in several processes including endosomal trafficking, actin organisation, maintenance of centrosome cohesion and transcription. In line with a more complex picture, multiple isoforms of the protein likely exist and non-centrosomal sites of localisation have been reported. This review outlines the evidence for both ciliary and extra-ciliary functions of ALMS1.

Pediatric pulmonology year in review 2017: Part 1

Pediatric Pulmonology publishes original research, case reports and review articles on topics related to a wide range of children's respiratory disorders. In this article (Part 1 of a series), we summarize the past year's publications in our major topic areas, as well as selected literature in these areas from other journals. In Part 1, we review selected articles on diagnostic testing/endoscopy, respiratory complications of neuromuscular disorders, and rare lung diseases.

To beat, or not to beat, that is question! The spectrum of ciliopathies

Cilia are widely distributed throughout the human body, and have numerous roles in physiology, development, and disease. Ciliary ultrastructure is complex, consisting of nine parallel microtubules doublets, with or without motor dynein arms and a central pair of microtubules. Classification of cilia has evolved over time, and currently, four main classes are described: motile and non-motile cilia with a "9 + 2" structure, and motile and non-motile cilia with a "9 + 0" structure, which depend on the presence or absence of dynein arms and a central pair. Ciliopathies are inherited multisystem disorders of cilia, and may present with a varied spectrum of genotypes and phenotypes. Motor and sensory ciliopathies were historically considered as distinct dysfunctions of motile and non-motile cilia, but recent data indicate that the classical features of motor and sensory cilia may overlap.