Feeding dystonia in McLeod syndrome

The protean presentations of XK disease (McLeod syndrome): a case series with new observations and updates on previously reported families

XK disease is a very rare, multi-system disease, which can present with a wide spectrum of symptoms. This disorder can also be identified pre-symptomatically with the incidental detection of serological abnormalities when typing erythrocytes in peripheral blood, or on other routine laboratory testing. Increasing awareness of this disorder and improved access to genetic testing are resulting in increasing identification of affected patients and families. Here we provide updates to some previously-reported families and patients and provide additional clinical details. We also report four new cases with a variety of presentations, one of whom had a novel mutation.

Systematic review of phenotypes in McLeod syndrome and case report of a progressive supranuclear palsy in a female carrier

INTRODUCTION

We present a systematic review of phenotypes of McLeod syndrome (MLS) and a case of a 73-year-old female carrier of the genetic alteration leading to MLS with the typical progressive supranuclear palsy (PSP) phenotype.

METHODS

To facilitate clinical reasoning and enable targeted diagnosis, we conducted a systematic review of the papers describing symptomatic cases of confirmed McLeod syndrome. This review follows the PRISMA 2020 statement: an updated guideline for reporting systematic reviews (Page et al in Syst Rev 10(1):89, 2021).

RESULTS

The average onset of MLS was at 40.2 years of age with chorea (46%), seizures and psychiatric changes (each 13%). Very common are weakened Kell antigen (100%), changes in muscle biopsy (100%), genetic alterations in XK (100%), elevated creatine kinase (97%), acanthocytes (96%), MRI changes (95%), chorea (84%) and hyporeflexia (82%).

CONCLUSION

This review of 65 males and 11 females gives a concise overview of clinical phenotypes in MLS, reinforcing our view that this female patient had PSP independent of MLS carrier status. This report highlights the pitfalls of anchoring in medical decision-making, particularly the possible diagnostic bias of a known genetic carrier status of a very rare disease.

Oromandibular dystonia – A systematic review

Oromandibular dystonia (OMD) is a clinical problem which is commonly encountered in the practice of movement disorders. OMD results from a variety of genetic and acquired etiologies and can occur as an isolated manifestation, or as part of an isolated generalized or a combined dystonia syndrome. There are only very few systematic reviews on this condition which often causes significant disability. We review here the etiology, clinical features, diagnostic approach and management of OMD.

Brain F-18 FDG and F-18 FP-CIT PET/CT Findings of c.856_860delCTCTA Mutation McLeod Syndrome

McLeod syndrome is a rare X-linked recessive genetic disorder that is caused by mutations of the XK gene. It is one of the core neuroacanthocytosis syndromes. We report the case of a 67-year-old man who presented to Kyungpook National University Hospital in the Republic of Korea with progressive worsening of generalized chorea and dystonia. He had no recognized family history of neurologic illness. A peripheral blood smear showed increased acanthocytes. His serum creatine kinase levels were 894 U/L. A brain MRI showed atrophy of the bilateral striatal nuclei. An F-18 F-N-(3-fluoropropyl)-2β-carboxymethoxy-3β-(4-iodophenyl) nortropane PET/CT showed moderately decreased dopamine transporter uptake in the putamen and severely decreased uptake in the caudate nucleus. An F-18 fludeoxyglucose PET/CT demonstrated markedly decreased metabolism at the caudate nucleus and the putamen. Whole exome sequencing revealed hemizygous pathogenic mutations of the XK gene (c.856_860delCTCTA;p.Leu286TyrfsTer16). We believe that these findings provide useful information regarding the clinical features of individuals with McLeod syndrome.

Childhood-Onset Spinocerebellar Ataxia 3: Tongue Dystonia as an Early Manifestation

Background

Dystonia is a relatively common feature of spinocerebellar ataxia 3 (SCA3). Childhood onset of SCA3 is rare and typically associated with either relatively large, or homozygous, CAG repeat expansions.

Case report

We describe a 10-year-old girl with SCA3, who presented with tongue dystonia in addition to limb dystonia and gait ataxia due to a heterozygous expansion of 84 repeats in ATXN3.

Discussion

Diagnosis of the SCAs can be challenging, and even more so in children. Tongue dystonia has not previously been documented in SCA3.

Huntington's disease-like disorders in Latin America and the Caribbean

Diseases with a choreic phenotype can be due to a variety of genetic etiologies. As testing for Huntington's disease (HD) becomes more available in previously resource-limited regions, it is becoming apparent that there are patients in these areas with other rare genetic conditions which cause an HD-like phenotype. Documentation of the presence of these conditions is important in order to provide appropriate diagnostic and clinical care for these populations. Information for this article was gathered in two ways; the literature was surveyed for publications reporting a variety of genetic choreic disorders, and movement disorders specialists from countries in Latin America and the Caribbean were contacted regarding their experiences with chorea of genetic etiology. Here we discuss the availability of molecular diagnostics for HD and for other choreic disorders, along with a summary of the published reports of affected subjects, and authors' personal experiences from the regions. While rare, patients affected by non-HD genetic choreas are evidently present in Latin America and the Caribbean. HD-like 2 is particularly prevalent in countries where the population has African ancestry. The incidence of other conditions is likely determined by other variations in ethnic background and settlement patterns. As genetic resources and awareness of these disorders improve, more patients are likely to be identified, and have the potential to benefit from education, support, and ultimately molecular therapies.

Management of Neuroacanthocytosis Syndromes

BACKGROUND

The two core neuroacanthocytosis (NA) syndromes, chorea-acanthocytosis (ChAc) and McLeod syndrome, are progressive neurodegenerative disorders that primarily affect the basal ganglia. The characteristic phenotype comprises a variety of movement disorders including chorea, dystonia, and parkinsonism, as well as psychiatric and cognitive symptoms attributable to basal ganglia dysfunction. These disorders are symptomatically managed on a case-by-case basis, with very few practitioners seeing more than a single case in their careers.

METHODS

A literature search was performed on PubMed utilizing the terms neuroacanthocytosis, chorea-acanthocytosis, and McLeod syndrome, and articles were reviewed for mentions of therapies, successful or otherwise.

RESULTS

There have been no blinded, controlled trials and only one retrospective case series describing ChAc. The various therapies that have been used in patients with NA syndromes are summarized.

DISCUSSION

Management remains at present purely symptomatic, which is similar in principle to other more common basal ganglia neurodegenerative disorders such as Huntington's disease (HD) and Parkinson's disease (PD). However, there are some specific issues particular to NA syndromes that merit attention. An integrated multidisciplinary approach is the ideal management strategy for these complex and multifaceted neurodegenerative disorders.

Untangling the Thorns: Advances in the Neuroacanthocytosis Syndromes

There have been significant advances in neuroacanthocytosis (NA) syndromes in the past 20 years, however, confusion still exists regarding the precise nature of these disorders and the correct nomenclature. This article seeks to clarify these issues and to summarise the recent literature in the field. The four key NA syndromes are described here-chorea-acanthocytosis, McLeod syndrome, Huntington's disease-like 2, and pantothenate kinase- associated neurodegeneration. In the first two, acanthocytosis is a frequent, although not invariable, finding; in the second two, it occurs in approximately 10% of patients. Degeneration affecting the basal ganglia is the key neuropathologic finding, thus the clinical presentations can be remarkably similar. The characteristic phenotype comprises a variety of movement disorders, including chorea, dystonia, and parkinsonism, and also psychiatric and cognitive symptoms attributable to basal ganglia dysfunction. The age of onset, inheritance patterns, and ethnic background differ in each condition, providing diagnostic clues. Other investigations, including routine blood testing and neuroimaging can be informative. Genetic diagnosis, if available, provides a definitive diagnosis, and is important for genetic counseling, and hopefully molecular therapies in the future. In this article I provide a historical perspective on each NA syndrome. The first 3 disorders, chorea-acanthocytosis, McLeod syndrome, Huntington's disease-like 2, are discussed in detail, with a comprehensive review of the literature to date for each, while pantothenate kinase-associated neurodegeneration is presented in summary, as this disorder has recently been reviewed in this journal. Therapy for all of these diseases is, at present, purely symptomatic.

Huntington's disease and Huntington's disease-like syndromes: an overview

PURPOSE OF REVIEW

The differential diagnosis of chorea syndromes may be complex and includes various genetic disorders such as Huntington's disease and mimicking disorders called Huntington's disease-like (HDL) phenotypes. To familiarize clinicians with these (in some cases very rare) conditions we will summarize the main characteristics.

RECENT FINDINGS

HDL disorders are rare and account for about 1% of cases presenting with a Huntington's disease phenotype. They share overlapping clinical features, so making the diagnosis purely on clinical grounds may be challenging, however presence of certain characteristics may be a clue (e.g. prominent orofacial involvement in neuroferritinopathy etc.), Information of ethnic descent will also guide genetic work-up [HDL2 in Black Africans; dentatorubral-pallidoluysian atrophy (DRPLA) in Japanese etc.], Huntington's disease, the classical HDL disorders (except HDL3) and DRPLA are repeat disorders with anticipation effect and age-dependent phenotype in some, but genetic underpinnings may be more complicated in the other chorea syndromes.

SUMMARY

With advances in genetics more and more rare diseases are disentangled, allowing molecular diagnoses in a growing number of choreic patients. Hopefully, with better understanding of their pathophysiology we are moving towards mechanistic therapies.

The differential diagnosis of Huntington's disease-like syndromes: 'red flags' for the clinician

A growing number of progressive heredodegenerative conditions mimic the presentation of Huntington's disease (HD). Differentiating among these HD-like syndromes is necessary when a patient with a combination of movement disorders, cognitive decline, behavioural abnormalities and progressive disease course proves negative to the genetic testing for HD causative mutations, that is, IT15 gene trinucleotide-repeat expansion. The differential diagnosis of HD-like syndromes is complex and may lead to unnecessary and costly investigations. We propose here a guide to this differential diagnosis focusing on a limited number of clinical features ('red flags') that can be identified through accurate clinical examination, collection of historical data and a few routine ancillary investigations. These features include the ethnic background of the patient, the involvement of the facio-bucco-lingual and cervical district by the movement disorder, the co-occurrence of cerebellar features and seizures, the presence of peculiar gait patterns and eye movement abnormalities, and an atypical progression of illness. Additional help may derive from the cognitive-behavioural presentation of the patient, as well as by a restricted number of ancillary investigations, mainly MRI and routine blood tests. These red flags should be constantly updated as the phenotypic characterisation and identification of more reliable diagnostic markers for HD-like syndromes progress over the following years.

Brain, blood, and iron: perspectives on the roles of erythrocytes and iron in neurodegeneration

The terms "neuroacanthocytosis" (NA) and "neurodegeneration with brain iron accumulation" (NBIA) both refer to groups of genetically heterogeneous disorders, classified together due to similarities of their phenotypic or pathological findings. Even collectively, the disorders that comprise these sets are exceedingly rare and challenging to study. The NBIA disorders are defined by their appearance on brain magnetic resonance imaging, with iron deposition in the basal ganglia. Clinical features vary, but most include a movement disorder. New causative genes are being rapidly identified; however, the mechanisms by which mutations cause iron accumulation and neurodegeneration are not well understood. NA syndromes are also characterized by a progressive movement disorder, accompanied by cognitive and psychiatric features, resulting from mutations in a number of genes whose roles are also basically unknown. An overlapping feature of the two groups, NBIA and NA, is the occurrence of acanthocytes, spiky red cells with a poorly-understood membrane dysfunction. In this review we summarise recent developments in this field, specifically insights into cellular mechanisms and from animal models. Cell membrane research may shed light upon the significance of the erythrocyte abnormality, and upon possible connections between the two sets of disorders. Shared pathophysiologic mechanisms may lead to progress in the understanding of other types of neurodegeneration.