Genetic testing of leukodystrophies unraveling extensive heterogeneity in a large cohort and report of five common diseases and 38 novel variants.

This study evaluates the genetic spectrum of leukodystrophies and leukoencephalopathies in Iran. 152 children, aged from 1 day to 15 years, were genetically tested for leukodystrophies and leukoencephalopathies based on clinical and neuroradiological findings from 2016 to 2019. Patients with a suggestive specific leukodystrophy, e. g. metachromatic leukodystrophy, Canavan disease, Tay-Sachs disease were tested for mutations in single genes (108; 71%) while patients with less suggestive findings were evaluated by NGS. 108 of 152(71%) had MRI patterns and clinical findings suggestive of a known leukodystrophy. In total, 114(75%) affected individuals had (likely) pathogenic variants which included 38 novel variants. 35 different types of leukodystrophies and genetic leukoencephalopathies were identified. The more common identified disorders included metachromatic leukodystrophy (19 of 152; 13%), Canavan disease (12; 8%), Tay-Sachs disease (11; 7%), megalencephalic leukodystrophy with subcortical cysts (7; 5%), X-linked adrenoleukodystrophy (8; 5%), Pelizaeus-Merzbacher-like disease type 1 (8; 5%), Sandhoff disease (6; 4%), Krabbe disease (5; 3%), and vanishing white matter disease (4; 3%). Whole exome sequencing (WES) revealed 90% leukodystrophies and genetic leukoencephalopathies. The total diagnosis rate was 75%. This unique study presents a national genetic data of leukodystrophies; it may provide clues to the genetic pool of neighboring countries. Patients with clinical and neuroradiological evidence of a genetic leukoencephalopathy should undergo a genetic analysis to reach a definitive diagnosis. This will allow a diagnosis at earlier stages of the disease, reduce the burden of uncertainty and costs, and will provide the basis for genetic counseling and family planning.

Lysosomal storage diseases.

Lysosomal storage diseases (LSDs) are a group of over 70 diseases that are characterized by lysosomal dysfunction, most of which are inherited as autosomal recessive traits. These disorders are individually rare but collectively affect 1 in 5,000 live births. LSDs typically present in infancy and childhood, although adult-onset forms also occur. Most LSDs have a progressive neurodegenerative clinical course, although symptoms in other organ systems are frequent. LSD-associated genes encode different lysosomal proteins, including lysosomal enzymes and lysosomal membrane proteins. The lysosome is the key cellular hub for macromolecule catabolism, recycling and signalling, and defects that impair any of these functions cause the accumulation of undigested or partially digested macromolecules in lysosomes (that is, 'storage') or impair the transport of molecules, which can result in cellular damage. Consequently, the cellular pathogenesis of these diseases is complex and is currently incompletely understood. Several LSDs can be treated with approved, disease-specific therapies that are mostly based on enzyme replacement. However, small-molecule therapies, including substrate reduction and chaperone therapies, have also been developed and are approved for some LSDs, whereas gene therapy and genome editing are at advanced preclinical stages and, for a few disorders, have already progressed to the clinic.

Gallbladder abnormalities in children with metachromatic leukodystrophy.

BACKGROUND: Metachromatic leukodystrophy (MLD) is a lysosomal storage disease that leads to neurological deterioration and visceral involvement, including sulphatide deposition in the gallbladder wall. Using our institution's extensive experience in treating MLD, we examined the incidence of gallbladder abnormalities in the largest cohort of children with MLD to date. METHODS: We conducted a retrospective review of all children with MLD, adrenoleukodystrophy (ALD), or Krabbe disease who underwent hematopoietic stem cell transplantation (HSCT) at our institution between 1994 and 2015. Baseline characteristics and unadjusted outcomes were compared using the Kruskal-Wallis test for continuous variables and Pearson χ2 test for categorical variables, with significance defined as P < 0.05. RESULTS: In total, 87 children met study criteria: 29 children with MLD and 58 children with ALD or Krabbe disease. Children with MLD were more likely to demonstrate gallbladder abnormalities on imaging, both before HSCT (41.4% versus 5.2%, P < 0.001) and after HSCT (75.9% versus 41.4%, P = 0.002). Consequently, a larger proportion of children with MLD underwent surgical or interventional management of biliary disease (10.3% versus 3.4%, P = 0.03). CONCLUSIONS: Children with MLD have a significantly greater incidence of gallbladder abnormalities than children with other lysosomal storage diseases. Biliary disease should be considered in children with MLD who develop abdominal pain, and cholecystectomy should be considered for persistent, symptomatic gallbladder abnormalities.

Developing therapeutic approaches for metachromatic leukodystrophy.

Metachromatic leukodystrophy (MLD) is an autosomal recessive lysosomal disorder caused by the deficiency of arylsulfatase A (ASA), resulting in impaired degradation of sulfatide, an essential sphingolipid of myelin. The clinical manifestations of MLD are characterized by progressive demyelination and subsequent neurological symptoms resulting in severe debilitation. The availability of therapeutic options for treating MLD is limited but expanding with a number of early stage clinical trials already in progress. In the development of therapeutic approaches for MLD, scientists have been facing a number of challenges including blood-brain barrier (BBB) penetration, safety issues concerning therapies targeting the central nervous system, uncertainty regarding the ideal timing for intervention in the disease course, and the lack of more in-depth understanding of the molecular pathogenesis of MLD. Here, we discuss the current status of the different approaches to developing therapies for MLD. Hematopoietic stem cell transplantation has been used to treat MLD patients, utilizing both umbilical cord blood and bone marrow sources. Intrathecal enzyme replacement therapy and gene therapies, administered locally into the brain or by generating genetically modified hematopoietic stem cells, are emerging as novel strategies. In pre-clinical studies, different cell delivery systems including microencapsulated cells or selectively neural cells have shown encouraging results. Small molecules that are more likely to cross the BBB can be used as enzyme enhancers of diverse ASA mutants, either as pharmacological chaperones, or proteostasis regulators. Specific small molecules may also be used to reduce the biosynthesis of sulfatides, or target different affected downstream pathways secondary to the primary ASA deficiency. Given the progressive neurodegenerative aspects of MLD, also seen in other lysosomal diseases, current and future therapeutic strategies will be complementary, whether used in combination or separately at specific stages of the disease course, to produce better outcomes for patients afflicted with this devastating inherited disorder.

Clinical epidemiologic characterization of orthopaedic and neurological manifestations in children with leukodystrophies.

BACKGROUND: Leukodystrophies (LKDs) are spectra of clinical conditions characterized primarily by brain white matter abnormalities. Although this condition was previously defined around inherited disorders of the white matter of the brain, current application includes acquired and sporadic conditions and some rare conditions that affect gray matter. Over the past 2 decades, information had become available on the clinical subtypes due to neurodiagnostic imaging and improvement in the genetic studies (cytogenetics and molecular genetics) of LKD. However, the epidemiologic profile of LKD remains largely unknown. We aimed in this study to characterize LKD by demographics, family history, orthopaedic and neurological manifestations, and clinical subtypes. METHODS: Trained medical personnel reviewed medical records of the study population diagnosed with LKD from 1986 to 2008. Using a retrospective review design, we determined the prevalence of the different clinical subtypes of LKD, family history, orthopaedic and neurological manifestations, and the demographics in LKD. The frequency and percentage (proportion, standard error, and 95% confidence interval for proportion) and the χ statistic and Fisher exact test for comparison of clinical subtypes were the statistical techniques used in the data analysis. RESULTS: Forty-four children were diagnosed with LKD between 1986 and 2008, of whom 25.0% had metachromatic LKD and 20.5% had Pelizaeus-Merzbacher LKD, whereas 40.9% were unspecified LKD. LKDs were more common among boys (63.6%), Whites (77.3%), and more likely to be diagnosed at age <3 years. Scoliosis (70.4%), hamstring contractures (81.8%), acquired hip dysplasia (88.6%), and equinus foot deformity (75.0%) were the most common orthopaedic manifestations. Common neurological manifestations were seizures (45.4%) and spasticity (77.3%). There was a statistically significant difference in sex and family history, seizures, hip dislocation, and hip subluxation, with respect to the clinical subtype of LKD, P<0.05. CONCLUSIONS: This epidemiologic characterization of LKD validates basic and clinical data on the familial history of LKD and its higher prevalence among boys. The orthopaedic manifestations common in LKD are scoliosis, hamstring contractures, acquired hip dysplasia, and equinus foot deformity, whereas common neurological manifestations are seizures and spasticity. These data are indicative of the need for orthopaedic surgeons to take into consideration this clinical epidemiologic aspect of LKD in the evaluation, treatment planning, and clinical expectations for these patients.

Juvenile metachromatic leukodystrophy: understanding the disease and implications for nursing care.

Hematopoietic stem cell transplants are increasingly being performed in attempt to halt the progression of juvenile metachromatic leukodystrophy, which is a rare neurodegenerative disease. Children who are diagnosed with metachromatic leukodystrophy are not commonly cared for by nurses who specialize in pediatric stem cell transplants. This article provides nurses with insight about this disease and serves as a guide for nursing care of this patient population during hematopoietic stem cell transplant. The case study highlights the complexities of care of this population while illustrating many of the unique care needs of patients with metachromatic leukodystrophy undergoing hematopoietic stem cell transplant. The article provides information about the pathophysiology of metachromatic leukodystrophy, the natural progression of symptoms, and how hematopoietic stem cell transplant may work to halt the progression of juvenile metachromatic leukodystrophy. It also focuses on the implications of nursing care, including a review of systems, the need for increased patient and family education, and the complexities of caring for a family with multiple affected children.

Early thalamic and cortical hypometabolism in adult-onset dementia due to metachromatic leukodystrophy.

A case of early-onset adult dementia with family history of dementia is reported, characterised by neuropsychological deficits, suggesting frontal involvement, with mild non specific white matter abnormalities on CT scan. Familial Alzheimer's disease was suspected but the neuropathological diagnosis on brain biopsy was metachromatic leukodystrophy. 18FDG-PET revealed a very peculiar pattern of metabolic impairment in thalamic areas, in medial and frontopolar regions, and in occipital lobes. Neuropsychological follow-up showed relatively stable difficulties of long-term memory and signs of frontal lobe dysfunction, similar to those observed in subcortical dementias. MRI subsequently showed periventricular leukoencephalopathy. The brain metabolic pattern observed in that case of metachromatic leukodystrophy was quite different from that reported in other types of dementia.