With a population of 1.4 billion, China shares the largest burden of rare genetic diseases worldwide. Current estimates suggest that there are over ten million individuals afflicted with chromosome disease syndromes and well over one million individuals with monogenic disease. Care of patients with rare genetic diseases remains a largely unmet need due to the paucity of available and affordable treatments. Over recent years, there is increasing recognition of the need for affirmative action by government, health providers, clinicians and patients. The advent of new next generation sequencing (NGS) technologies such as whole genome/exome sequencing, offers an unprecedented opportunity to provide large-scale population screening of the Chinese population to identify the molecular causes of rare genetic diseases. As a surrogate for lack of effective treatments, recent development and implementation of noninvasive prenatal testing (NIPT) in China has the greatest potential, as a single technology, for reducing the number of children born with rare genetic diseases.
The fragile X mental retardation 1 gene, which codes for the fragile X mental retardation 1 protein, usually has 5 to 40 CGG repeats in the 5' untranslated promoter. The full mutation is the almost always the cause of fragile X syndrome (FXS). The prevalence of FXS is about 1 in 4,000 to 1 in 7,000 in the general population although the prevalence varies in different regions of the world. FXS is the most common inherited cause of intellectual disability and autism. The understanding of the neurobiology of FXS has led to many targeted treatments, but none have cured this disorder. The treatment of the medical problems and associated behaviors remain the most useful intervention for children with FXS. In this review, we focus on the non-pharmacological and pharmacological management of medical and behavioral problems associated with FXS as well as current recommendations for follow-up and surveillance.
Fragile X syndrome (FXS) is the most common inherited form of intellectual disability, and is the leading single-gene cause of autism spectrum disorders. It is due to a loss of the fragile X mental retardation protein, which leads to molecular, behavioral, and cognitive deficits in these patients. Improvements in our understanding of its pathophysiology have led to the development of numerous targeted treatments in FXS as highlighted by metabotropic glutamate receptor antagonists and gamma-Aminobutyric acid receptor modulators. This review will summarize relevant pre-clinical data and results from clinical trials in human subjects with FXS. It will also highlight upcoming studies and future directions for clinical trials as well.
Facioscapulohumeral muscular dystrophy (FSHD) is an inherited autosomal dominant disorder characterized clinically by progressive muscle degeneration. Currently, no curative treatment for this disorder exists. FSHD patients are managed through physiotherapy to improve function and quality of life. Over the last two decades, FSHD has been better understood as a disease genetically characterized by a pathogenic contraction of a subset of macrosatellite repeats on chromosome 4. Specifically, several studies support an FSHD pathogenesis model involving the aberrant expression of the double homeobox protein 4 (DUX4) gene. Hence, potential therapies revolving around inhibition of DUX4 have been explored. One of the potential treatment options is the use of effective antisense oligonucleotides (AOs) to knockdown expression of the myopathic DUX4 gene and its downstream molecules including paired-like homeodomain transcription factor 1 (PITX1). Success in the suppression of PITX1 expression has already been demonstrated systemically in vivo in recent studies. In this article, we will review the pathogenesis of FSHD and the latest research involving the use of antisense knockdown therapy.
Heart failure is one of the leading causes of death in developed nations. End stage heart failure often requires cardiac transplantation for survival. The left ventricular assist device (LVAD) has been one of the biggest evolvements in heart failure management often serving as bridge to transplant or destination therapy in advanced heart failure. Like any other medical device, LVAD is associated with complications with infections being reported in many patients. Endocarditis developing secondary to the placement of LVAD is not a frequent, serious and difficult to treat condition with high morbidity and mortality. Currently, there are few retrospective studies and case reports reporting the same. In our review, we found the most common cause of endocarditis in LVAD was due to bacteria. Both bacterial and fungal endocarditis were associated with high morbidity and mortality. In this review we will be discussing the risk factors, organisms involved, diagnostic tests, management strategies, complications, and outcomes in patients who developed endocarditis secondary to LVAD placement.
Peripheral T-cell lymphoma (PTCL) is a set of rare and highly heterogeneous group of mature T- and NK-cell neoplasms associated with poor outcomes and lack of standard and effective therapies. The total number of newly diagnosed cases of PTCL yearly in China is estimated about 50,000. Chidamide (CS055) is a novel and orally active benzamide class of histone deacetylase (HDAC) inhibitor that selectively inhibits activity of HDAC1, 2, 3 and 10, the enzymes that are involved and play an important role in tumor initiation and development in both tumor cells and their surrounding micro-environment. Functioning as a genuine epigenetic modulator, chidamide induces growth arrest and apoptosis in tumor cells and enhances cellular antitumor immunity. Based on the overall results from preclinical and phase I clinical studies, exploratory and pivotal phase II trials of chidamide for relapsed or refractory PTCL were conducted from March 2009 to May 2012, and the results led to CFDA approval of chidamide for the indication in December 2014, being the first approved orphan drug according to the research & development approach of orphan drugs in China, as well as the first orally active drug for PTCL in China and worldwide.
Rare diseases with a low prevalence are a key public health issue because the causes of those diseases are difficult to determine and those diseases lack a clearly established or curative treatment. Thus, investigating the molecular mechanisms that underlie the pathology of rare diseases and facilitating the development of novel therapies using disease models is crucial. Human induced pluripotent stem cells (iPSCs) are well suited to modeling rare diseases since they have the capacity for self-renewal and pluripotency. In addition, iPSC technology provides a valuable tool to generate patient-specific iPSCs. These cells can be differentiated into cell types that have been affected by a disease. These cells would circumvent ethical concerns and avoid immunological rejection, so they could be used in cell replacement therapy or regenerative medicine. To date, human iPSCs could have been generated from multiple donor sources, such as skin, adipose tissue, and peripheral blood. However, these cells are obtained via invasive procedures. In contrast, several groups of researchers have found that urine may be a better source for producing iPSCs from normal individuals or patients. This review discusses urinary iPSC (UiPSC) as a candidate for modeling rare diseases. Cells obtained from urine have overwhelming advantages compared to other donor sources since they are safely, affordably, and frequently obtained and they are readily obtained from patients. The use of iPSC-based models is also discussed. UiPSCs may prove to be a key means of modeling rare diseases and they may facilitate the treatment of those diseases in the future.
A number of persons with an intractable disease (ID) experience work-related problems that could lead to job loss. The aim of this study was to ascertain perceptions regarding a range of work-related issues and corresponding support needs of individuals with an ID. Potential participants were people ages 15 to 64 with one of the 130 intractable chronic diseases designated in the Act to Comprehensively Support the Daily and Social Activities of Persons with Disabilities (Comprehensive Support for the Disabled Act). Participants completed a self-administered questionnaire. With the assistance of patients' organizations, 3,000 questionnaires were mailed to potential participants. Questions included demographic characteristics, family concerns, employment/supported employment, work accommodations, and other aspects of life. Responses were received from 889 (29.6%) participants, and respondents had 57 IDs. Forty-six-point-seven percent of respondents reported being unemployed due to fatigue and/or long-term treatment. Nearly half of the unemployed respondents reported that they had been unable to work despite their willingness to do so. Common requests for accommodation included flexible work hours, working at home, and job/workplace modifications. Only 30% of respondents knew about job training programs and supported work available for persons with disabilities. The results of the study are relevant for employees, employers, and occupational health/human resource professionals. The issue of reasonable accommodations for persons with an ID needs to be addressed in future research in order to promote continued work by those persons.
Alcohol use disorders (AUDs) have been reported in a limited number of individuals with cognitive impairment but rarely in those with fragile X syndrome (FXS). However, in Colombia, culturally, alcohol consumption is very common. Here, we report eight cases of patients with FXS who have frequent alcohol consumption in Ricaurte, Colombia. Some of these patients have also used tobacco and illegal substances, including cocaine, which use has not been previously reported in those with FXS. Alcohol and substance use dependence is associated with exacerbation of their behavioral problems, such as increased impulsivity and aggression, as well as of medical problems such as an increased frequency of seizures.
Allan-Herndon-Dudley syndrome (AHDS) is an X-linked disorder caused by impaired thyroid hormone transporter. Patients with AHDS usually exhibit severe motor developmental delay, delayed myelination of the brain white matter, and elevated T3 levels in thyroid tests. Neurological examination of two patients with neurodevelopmental delay revealed generalized hypotonia, and not paresis, as the main neurological finding. Nystagmus and dyskinesia were not observed. Brain magnetic resonance imaging demonstrated delayed myelination in early childhood in both patients. Nevertheless, matured myelination was observed at 6 years of age in one patient. Although the key finding for AHDS is elevated free T3, one of the patients showed a normal T3 level in childhood, misleading the diagnosis of AHDS. Genetic analysis revealed two novel SLC16A2 mutations, p.(Gly122Val) and p.(Gly221Ser), confirming the AHDS diagnosis. These results indicate that AHDS diagnosis is sometimes challenging owing to clinical variability among patients.
Colonic polyps are usually asymptomatic, and are commonly detected during screening colonoscopy. Severe hypokalemia secondary to secretory diarrhea is a rare presentation of rectal polyps. We present a 70 years old female with hypokalemia and acute kidney injury secondary to secretory diarhea due to moderately differentiated adenocarcinoma of rectum, all of which is syndromically sometimes referred to as McKittrick and Wheelock syndrome. The case is presented because McKittrick-Wheelock syndrome is still more uncommon with malignancy. The syndrome may be associated with other features of hypersecretory diarrhea. Though very rare, clinical suspicion would often lead to diagnosis and appropriate management. We also review the previously published reports of this entity.
Coffin-Siris syndrome (CSS) (MIM 135900) is characterized by developmental delay, severe speech impairment, distinctive facial features, hypertrichosis, aplasia or hypoplasia of the distal phalanx or nail of the fifth digit and agenesis of the corpus callosum. Recently, it was shown that mutations in the ARID1B gene are the main cause of CSS, accounting for 76% of identified mutations. Here, we report a 15 year-old female patient who was admitted to our clinic with seizures, speech problems, dysmorphic features, bilaterally big, large thumb, café-au-lait (CAL) spots, obesity and hyperinsulinism. First, the patient was thought to have an association of neurofibromatosis and Rubinstein Taybi syndrome. Because of the large size of the NF1 gene for neurofibromatosis and CREBBP gene for Rubinstein Taybi syndrome, whole exome sequence analysis (WES) was conducted and a novel ARID1B mutation was identified. The proband WES test identified a novel heterozygous frameshift mutation c.3394_3395insTA in exon 13 of ARID1B (NM_017519.2) predicting a premature stop codon p.(Tyr1132Leufs*67). Sanger sequencing confirmed the heterozygous c.3394_3395insTA mutation in the proband and that it was not present in her parents indicating de novo mutation. Further investigation and new cases will help to understand this phenomenon better.
We report an unusual case of recurrent encephalopathy due to acquired hemophagocytic lymphohistiocytosis (HLH) in a patient with propionic acidemia (PA). PA is an inherited metabolic disorder in which patients often present with encephalopathy and pancytopenia during metabolic decompensation. However, these patients may rarely develop HLH with similar presentation. This case illustrates the need to distinguish HLH induced encephalopathy from the one secondary to metabolic decompensation in these patients, as early diagnosis and treatment of HLH improves prognosis. This case also highlights the importance of considering HLH in patients presenting with unexplained encephalopathy, as early diagnosis and treatment is lifesaving in this otherwise lethal condition. To our knowledge this is the first case report of acquired HLH presenting as recurrent encephalopathy followed by complete recovery, in a metabolically stable patient with PA.
Adventitial cystic disease (ACD) of the common femoral vein is a rare vascular disorder. It becomes more difficult to recognize preoperatively especially when the femoral vein is affected. We report the case of a 62-year-old female patient who presented with a one-month history of painless swelling in her right lower extremity. She had no specific past medical history and no history of trauma, and had a full coagulopathy profile that was negative for any hypercoagulable syndrome. On examination, her lower right leg was significantly swollen with a palpable mass in her right inguinal region. A computerized tomography (CT) with contrast was performed to provide more information and revealed an eccentric compression over the medial wall of the right common femoral vein. During surgical exploration, adventitial cystic mucinous disease was enucleated and the patient underwent femoral exploration, excision of the cysts and reconstruction of iliac femoral vein graft using an artificial blood vessel. The pathological examination confirmed the diagnosis. The patient continued to do well, and she had an unremarkable venous duplex evaluation at her 6-month follow-up. The presentation, investigation, treatment, and pathology of this condition are discussed with a literature review.
We report a 12-year-old male with Prader-Willi syndrome (PWS) and 47, XYY syndrome. Genetic work up revealed 47, XYY karyotype. PWS diagnosis was made by polymerase chain reaction methylation and maternal uniparental disomy (mUPD) was determined to be the etiology. Review of distinct behavioral features, possible interplay between the two syndromes and considerations for diagnoses are presented. To our knowledge, this is the first report of behavioral features in PWS with comorbid 47, XYY.
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