A case of McLeod phenotype of neuroacanthocytosis brain MR features and literature review

Abstract

Huntington's disease and neuroacanthocytosis may present similar clinical and MRI features. It is important to differentiate these findings since treatment and prognosis vary vastly between them. The aim of this article is to familiarize radiologists with the differentiating features of Huntington's disease and various diseases comprising neuroacanthocytosis. A 40-year-old Indian man with extrapyramidal symptoms was referred for MRI. The clinical diagnosis was Huntington's disease, but there were a few atypical clinical features such as a history of biting the tongue, tics, marked hyporeflexia and lower limb muscle wasting. MR showed atrophy of the caudate nucleus and putamen with iron deposition in the basal ganglia, which can be seen in Huntington's disease and in neuroacanthocytosis. An increased blood acanthocyte level was subsequently confirmed. Further work-up revealed increased serum creatine phosphokinase levels, normal serum lipoprotein levels and depressed K cell antigen activity on serological studies, confirming the diagnosis of McLeod syndrome. McLeod syndrome is one of the distinct phenotypes of neuroacanthocytosis. Neuroacanthocytosis is a group of disorders with increased serum acanthocyte counts and neurological involvement. Various causes of neuroacanthocytosis are discussed. It is important to consider the possibility of neuroacanthocytosis when features typical of Huntington's disease are encountered on imaging.

Figure 1

MR SE axial T1- (A) and T2-weighted (B) images show atrophy of the caudate nucleus and putamen (arrows) with a subtle increase in signal intensity changes on T2-weighted images causing minimal frontal horn dilatation bilaterally. Minimal cerebral atrophy is also observed.

Figure 2

MR FLAIR coronal images (A, B) show striatal atrophy and hypointensity in the lentiform nuclei (small arrows) suggesting iron deposition. Also note minimal generalized cerebral atrophy and minimal cerebral peduncle thinning (thick arrow).

Figure 3

Other described imaging features in neuroacanthocytosis in other cases. A) FLAIR axial brain image in a patient with pentothenate kinase-associated neurodegeneration, showing the typical “eye of a tiger” appearance with peripheral hypointen-sity due to iron deposition and central hyperintensity due to gliosis. T2-weighted axial brain images showing increased iron deposition in the globus pallidus (B) and neostriatal (putamen and caudate nucleus) hyperintensities (C). D) Sagittal T2-weighted image of the cervical spine showing dorsal tract hyperintensities in a case of abetalipoproteinaemia (see Table 1).