Ans. is 'a' i.e., Hallervorden spatz disease o Neurodegeneration with brain iron accumulation (NB1A) is a rare progressive neurodegenerative syndrome that causes parkinsonism, dystonia, cognitive decline, and other neurologic deficits.Pantothenate kinase-associated neurodesenerationso Pantothenate kinase-associated neurodegeneration (PKAN), formerly known as HaUervorden-Snat?. disease, is an autosomal recessive disorder; most cases are caused by mutations in the gene encoding pantothenate kinase 2 (PANK2).o PANK2 catalyses the rate limiting step in the synthesis of coenzy>me A from vitamin B5.o PKAN is included in a group of disorders known as neurodegeneration with brain iron accumulation (NBIA).o NBIA is now considered a spectrum of phenotvpicallv overlapping disorders, with several subtypes defined bv differences at the molecular eenetic level, includins the following :Pantothenate kinase-associated neurodegeneration a Infantile neuroaxonal dystrophyMitochondrial membrane protein-associated neurodegenerationBeta-propeller protein-associated neurodegenerationFatty acid hydroxylase-associated neurodegenerationKufor-Rakeb syndromeNeuroferritinopathyAceruloplasminemiaWoodhouse-Sakati syndromeNBIA of unknown causeClinical featuresChildren with NBIA have posture and gait abnormalities.Bradykinesia, rigidity, and other parkinsonian features, including tremor.Affected patients may also have hyperkinetic movement disorders, such as dystonia and choreoathetosis, as well as progressive dysarthria, dementia, ataxia, spasticity, epilepsy, optic atrophy, and retinitis pigmentosa.Pantothenate kinase associated neurodeeeneration (tlallervorden Spatz disease)o Many patients with NBIA have mutations in the gene encoding pantothenate kinase 2 (PANK2) and are said to have pantothenate kinase-associated neurodegeneration (PKAN).o PK.4N is inherited in an autosomal recessive pattern,o Two variants were distinguished:Classic disease with early onset (typically in the first decade of life) and rapid progression.Atypical disease with later onset (usually in the second or third decade o f life) and slow progression.All patients with classic disease and one-third of those with atypical disease had PANK2 mutations. In this series, abnormalities in classic NBIA were noted with the following frequencies:o Extrapyramidal signs including dystonia, dysarthria, rigidity, and choreoathetosis - 98 percento Retinopathy - 68 percento Cognitive decline - 29 percento Corticospinal tract involvement, including spasticity, hyperreflexia, and extensor toe signs - 25 percento Few patients had optic atrophy (3 percent) and none had seizures.Neuroimasineo All patients with RANK2 mutations, whether classic or atypical, had the characteristic radiologic sign known as "eve of the tiger" on brain MRI, with a central focus of increased T2 signal intensity in the medial globus paliidus surrounded by a zone of decreased signal.o This sign was not seen in patients without RANK2 mutations. While considered a characteristic feature of PKAN, the eye of the tiger sign has also been reported in a minority of patients with neuroferritinopathy.o In addition to iron distribution within the globus paliidus and substantia nigra, other typical MRI features vary according to the type of NBIA:# Pantothenate kinase-associated neurodegeneration-Eye of the tiger sign.# Infantile neuroaxonal dystrophy-Cerebellar atrophy; some cases lack iron deposition.# Mitochondrial membrane protein-associated neurodegen eration-Cerebellar and cortical atrophy and T2- weighted hyperintense streaking between the globus pallidus interna and externa.# Beta-propeller protein-associated neurodegeneration-TI-weighted signal hyperintensity with a central band of hypointensity within the substantia nigra.