Panthotenate Kinase-Associated Neurodegeneration Has a Founder Mutation (c.215_216insa) in Indian Agrawal Patients

Clinical, imaging and genetic profile of twenty-four patients with pantothenate kinase-associated neurodegeneration (PKAN)- A single centre study from India

INTRODUCTION

Pantothenate kinase-associated neurodegeneration (PKAN) is the most common "Neurodegeneration with Brain Iron Accumulation" disorder. This study aimed to study the clinical, radiological and genetic profiling of a large cohort of patients with PKAN.

METHODS

This is an ambispective hospital-based single centre study conducted at a tertiary care centre from India. After tabulating the clinical details, appropriate rating scales were applied followed by magnetic resonance imaging brain and exome sequencing. The segregation of the causal variants in the families were analysed using Sanger sequencing.

RESULTS

Twenty-four patients (14 males) with a median age at initial examination of 13 years (range: 4-54 years) and age at onset of 8 years (range: 0.5-40 years) were identified. Almost two-thirds (62%) had onset before 10 years. Difficulty walking was the most common presenting symptom (41.6%) and dystonia was the most common extrapyramidal phenomenology (100%) followed by parkinsonism (54.2%). Retinitis pigmentosa was present in 37.5% patients. MRI showed hypo intensity on T2 and SWI sequences in globus pallidus (100%), substantia nigra (70.8%) and red nucleus (12.5%). Eye-of-the-tiger sign was present in 95.8%. Biallelic variants in PANK2 gene was identified in all 20 patients who underwent genetic testing. Among the 18 unique variants identified in these 20 patients 10 were novel. Sanger sequencing confirmed the segregation of the mutation in the available family members.

CONCLUSIONS

Wide range of age at onset was noted. Dystonia at presentation, pathognomonic eye-of-tiger sign, and disease-causing variants in PANK2 gene were identified in nearly all patients. Ten novel variants were identified expanding the genotypic spectrum of PKAN.

Neurodegeneration with brain iron accumulation: Characterization of clinical, radiological, and genetic features of pediatric patients from Southern India

BACKGROUND

Neurodegeneration with brain iron accumulation (NBIA) is a group of rare inherited neurodegenerative disorders. Ten types of NBIA are known. Studies reporting various NBIA subtypes together are few. This study was aimed at describing clinical features, neuroimaging findings, and genetic mutations of different NBIA group disorders.

METHODS

Clinical, radiological, and genetic data of patients diagnosed with NBIA in a tertiary care centre in Southern India from 2014 to 2020 was retrospectively collected and analysed.

RESULTS

In our cohort of 27 cases, PLA2G6-associated neurodegeneration (PLAN) was most common (n = 13) followed by Pantothenate kinase-associated neurodegeneration (PKAN) (n = 9). We had 2 cases each of Mitochondrial membrane-associated neurodegeneration (MPAN) and Beta-propeller protein- associated neurodegeneration (BPAN) and 1 case of Kufor-Rakeb Syndrome (KRS). Walking difficulty was the presenting complaint in all PKAN cases, whereas the presentation in PLAN was that of development regression with onset at a mean age of 2 years. Overall, 50% patients of them presented with development regression and one-third had epilepsy. Presence of pyramidal signs was most common examination feature (89%) followed by one or more eye findings (81%) and movement disorders (50%). Neuroimaging was abnormal in 24/27 cases and cerebellar atrophy was the commonest finding (52%) followed by globus pallidus hypointensities (44%).

CONCLUSIONS

One should have a high index of clinical suspicion for the diagnosis of NBIA in children presenting with neuroregression and vision abnormalities in presence of pyramidal signs or movement disorders. Neuroimaging and ophthalmological evaluation provide important clues to diagnosis in NBIA syndromes.

Founder variants and population genomes-Toward precision medicine

Human migration and community specific cultural practices have contributed to founder events and enrichment of the variants associated with genetic diseases. While many founder events in isolated populations have remained uncharacterized, the application of genomics in clinical settings as well as for population scale studies in the recent years have provided an unprecedented push towards identification of founder variants associated with human health and disease. The discovery and characterization of founder variants could have far reaching implications not only in understanding the history or genealogy of the disease, but also in implementing evidence based policies and genetic testing frameworks. This further enables precise diagnosis and prevention in an attempt towards precision medicine. This review provides an overview of founder variants along with methods and resources cataloging them. We have also discussed the public health implications and examples of prevalent disease associated founder variants in specific populations.

Review: Understanding Rare Genetic Diseases in Low Resource Regions Like Jammu and Kashmir - India

Rare diseases (RDs) are the clinical conditions affecting a few percentage of individuals in a general population compared to other diseases. Limited clinical information and a lack of reliable epidemiological data make their timely diagnosis and therapeutic management difficult. Emerging Next-Generation DNA Sequencing technologies have enhanced our horizons on patho-physiological understanding of many of the RDs and ushered us into an era of diagnostic and therapeutic research related to this ignored health challenge. Unfortunately, relevant research is meager in developing countries which lack a reliable estimate of the exact burden of most of the RDs. India is to be considered as the "Pandora's Box of genetic disorders." Owing to its huge population heterogeneity and high inbreeding or endogamy rates, a higher burden of rare recessive genetic diseases is expected and supported by the literature findings that endogamy is highly detrimental to health as it enhances the degree of homozygosity of recessive alleles in the general population. The population of a low resource region Jammu and Kashmir (J&K) - India, is highly inbred. Some of its population groups variably practice consanguinity. In context with the region's typical geographical topography, highly inbred population structure and unique but heterogeneous gene pool, a huge burden of known and uncharacterized genetic disorders is expected. Unfortunately, many suspected cases of genetic disorders remain undiagnosed or misdiagnosed due to lack of appropriate clinical as well as diagnostic resources in the region, causing patients to face a huge psycho-socio-economic crisis and many a time suffer life-long with their ailment. In this review, the major challenges associated with RDs are highlighted in general and an account on the methods that can be adopted for conducting fruitful molecular genetic studies in genetically vulnerable and low resource regions is also provided, with an example of a region like J&K - India.