Objective: To correlate, clinical and magnetic resonance imaging (MRI) characteristics, of patients with neurodegeneration with brain iron accumula­tion (NBIA), with genetics and establish genotype-phenotype correlations

Background: NBIA, a group of neurodegenerative disorders with excess iron predominantly in basal ganglia, substantia nigra (SN), red nucleus (RN) and dentate nucleus (DN) is clinically and genetically heterogenous[1,2].

Method: 18 patients from a single center in South India, with extra pyramidal features, spasticity, seizures and neuropsychiatric abnormalities in varying combinations with MRI evidence of iron deposition were included. Ancillary investigations such as serum ceruloplasmin, ferritin, blood sugar levels, hormonal profile, smear for acanthocytes, fundus/slit lamp examination for KF ring, neuropsychological assessment, electroencephalogram and nerve conduction study were done according to the clinical presentation. Target gene sequencing was done for the 10 known genes of NBIA.

Results: 11/18 patients were males with age of onset ranging from 2-63 years (23.94±17.71)(fig 1). 7 were consanguineous born and 5 had a positive family history.  First symptom was dystonia in 13 (12 limb onset, 1 lingual), parkinsonism in 3, chorea in 1 and ataxia in 1. Over the course of illness 16 had dystonia, 8 had parkinsonism, 2 each had ataxia and myoclonus, 1 each had chorea and hand stereotypies (fig 2). Oculomotor abnormalities (the most common associated feature) included slow saccades (11), oculomotor apraxia (1) and eyelid opening apraxia (1). Neuropsychiatric symptoms (4), pyramidal signs (3), optic disc pallor (2), seizures (2) and retinal pigmentary degeneration (1) followed (fig 3). All had iron deposition in globus pallidus, detected on susceptibility weighted images (SWI) , SN blooming in 9, combined RN, DN and striatum in 3 (fig 4). Two had classical “eye of the tiger” sign, 3 had bilateral white matter hyperintensities. Targeted gene sequencing showed mutations in PANK2 (2), PLA2G6 (2), WDR45 (1), FA2H (1), ATP13A2 (1), DCAF17(2), CP (1) and 9 tested negative of whom clinical exome sequencing showed mutations in KMT2B, XPR2, SNCB in one patient each.

Conclusion: KMT2B, XPR2, SNCB can manifest like NBIA and this large case series gives insights into the clinico-genetic correlations. Newer gene discoveries may widen the spectrum of NBIA as many patients may test negative in the targeted panel.

References: [1] Hogarth P. Neurodegeneration with Brain Iron Accumulation: Diagnosis and Management. J Mov Disord. 2015 Jan;8(1):1–13.
[2] Meyer E, Kurian MA, Hayflick SJ. Neurodegeneration with Brain Iron Accumulation: Genetic Diversity and Pathophysiological Mechanisms. Annu Rev Genomics Hum Genet. 2015;16(1):257–79.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/clinicalimaging-and-genetic-correlations-in-a-neuronal-brain-iron-accumulation-cohort-from-india/