Infantile neuroaxonal dystrophy caused by uniparental disomy

Successful clinical application of pre-implantation genetic diagnosis for infantile neuroaxonal dystrophy

Infantile neuroaxonal dystrophy (INAD) is a rare, lethal, autosomal recessive neurodegenerative disease and leads to progressive impairment of movement and cognition. A couple with a proband child with calcium-independent group VI phospholipase A2 (PLA2G6)-associated INAD and a previous affected pregnancy sought pre-implantation genetic diagnosis (PGD) to bear a healthy child. Intracytoplasmic sperm injection treatment was performed and 15 blastocystic embryos were obtained at days 5 and 6, and these biopsies were amplified. PGD was performed by next-generation sequencing-based linkage analysis in conjunction with aneuploidy screening. Only two embryos were considered for transfer. In the second frozen-thawed embryo transfer cycle, transfer of a mosaic PLA2G6 c.692G>T heterozygous embryo resulted in a singleton ongoing pregnancy. Prenatal diagnosis was performed using amniotic fluid cells, providing results consistent with those of PGD. The aneuploidy screen and karyotype analysis indicated that the chromosomes of the fetus were normal without any mosaicism. The present study reported the first successful PGD for INAD. For parents at risk, this strategy may successfully lead to pregnancies with embryos unlikely to develop INAD, thus providing valuable experience in reproductive management regarding INAD and potentially other single-gene disorders.

Atypical Childhood-onset Neuroaxonal Dystrophy in an Indian Girl

A 7-year-old girl presented with progressive walking difficulties, spasticity, and cognitive decline with onset at 3 years of age. No seizures, vision, or hearing impairment were reported. The magnetic resonance imaging of the brain revealed cerebellar atrophy and evidence of iron deposition in the globi pallidi and substantia nigra. The clinico-radiological profile was suggestive of atypical childhood-onset neuroaxonal dystrophy. The patient was found to have compound heterozygous mutations in the PLA2G6 gene confirming the diagnosis.

Monozygotic twins with infantile neuroaxonal dystrophy: A case report and literature review

Infantile neuroaxonal dystrophy (INAD) is a rare neurodegenerative disease with early onset. PLA2G6 gene mutations have been identified in the majority individuals with INAD. In future, molecular diagnosis of INAD will replace the invasive biopsies used previously. In the present report, monozygotic male twins with INAD were referred The Children's Hospital (Zhejiang University School of Medicine, Zhejiang, China) at fifteen months old for delayed development. The older brother was found to have developmental stagnation when he was 6 months old. The patient could not stand securely without support, and had poor eye tracking and listening ability. Magnetic resonance imaging (MRI) of the patient's brain revealed cerebellar atrophy and electromyography identified signs of peripheral neuropathy. The younger brother displayed similar clinical features and findings. Two different phospholipase A2 group VI (PLA2G6; 22q13.1) gene mutations were detected in the twins by DNA sequencing. The results of the present study indicate that neurogenetic disease should be considered when child patients present with idiopathic developmental stagnation, particularly when similar cases have appeared in the same family. In addition, INAD should be considered as a possible diagnosis when the patient has developmental delay of the central and peripheral nerves. In the future, molecular genetic testing will be the primary method of INAD diagnosis, enabling better prevention of this genetic disease.

Validation of the finding of hypertrophy of the clava in infantile neuroaxonal dystrophy/PLA2G6 by biometric analysis

INTRODUCTION

Infantile neuroaxonal dystrophy (INAD), an autosomal recessive neurodegenerative disorder due to PLA2G6 mutation, is classified both as a PLA2G6-associated neurodegeneration (PLAN) disorder and as one of the neurodegeneration with brain iron accumulation (NBIA) disorders. Age of onset and clinical presentation in INAD is variable. Typically described imaging features of cerebellar atrophy, cerebellar cortex bright FLAIR signal, and globus pallidus iron deposition are variable or late findings. We characterize clinical and neuroimaging phenotypes in nine children with confirmed PLA2G6 mutations and show a useful imaging feature, clava hypertrophy, which may aid in earlier identification of patients. Measurements of the clava confirm actual enlargement, rather than apparent enlargement due to volume loss of the other brain stem structures.

METHODS

A retrospective clinical and MRI review was performed. Brain stem measurements were performed and compared with age-matched controls.

RESULTS

We identified nine patients, all with novel PLA2G6 gene mutations. MRI, available in eight, showed clava hypertrophy, regardless of age or the absence of other more typically described neuroimaging findings. Brain autopsy in our cohort confirmed prominent spheroid bodies in the clava nuclei.

CONCLUSION

Clava hypertrophy is an important early imaging feature which may aid in indentification of children who would benefit from specific testing for PLA2G6 mutations.

Genetic Analysis of PLA2G6 in 22 Indian Families with Infantile Neuroaxonal Dystrophy, Atypical Late-Onset Neuroaxonal Dystrophy and Dystonia Parkinsonism Complex

Mutations in PLA2G6 were identified in patients with a spectrum of neurodegenerative conditions, such as infantile neuroaxonal dystrophy (INAD), atypical late-onset neuroaxonal dystrophy (ANAD) and dystonia parkinsonism complex (DPC). However, there is no report on the genetic analysis of families with members affected with INAD, ANAD and DPC from India. Therefore, the main aim of this study was to perform genetic analysis of 22 Indian families with INAD, ANAD and DPC. DNA sequence analysis of the entire coding region of PLA2G6 identified 13 different mutations, including five novel ones (p.Leu224Pro, p.Asp283Asn, p.Arg329Cys, p.Leu491Phe, and p.Arg649His), in 12/22 (54.55%) families with INAD and ANAD. Interestingly, one patient with INAD was homozygous for two different mutations, p.Leu491Phe and p.Ala516Val, and thus harboured four mutant alleles. With these mutations, the total number of mutations in this gene reaches 129. The absence of mutations in 10/22 (45.45%) families suggests that the mutations could be in deep intronic or promoter regions of this gene or these families could have mutations in a yet to be identified gene. The present study increases the mutation landscape of PLA2G6. The present finding will be useful for genetic diagnosis, carrier detection and genetic counselling to families included in this study and other families with similar disease condition.