Benign hereditary chorea, not only chorea: a family case presentation

A Novel Missense Variant in the NKX2-1 Homeodomain Prevents Transcriptional Rescue by TAZ

Background: Brain-lung-thyroid syndrome (BLTS) is caused by NKX2-1 haploinsufficiency, resulting in chorea/choreoathetosis, respiratory problems, and hypothyroidism. Genes interacting with NKX2-1 mutants influence its phenotypic variability. We report a novel NKX2-1 missense variant and the modifier function of TAZ/WWTR1 in BLTS. Methods: A child with BLTS underwent next-generation sequencing panel testing for thyroid disorders. His family was genotyped for NKX2-1 variants and screened for germline mosaicism. Mutant NKX2-1 was generated, and transactivation assays were performed on three NKX2-1 target gene promoters. DNA binding capacity and protein-protein interaction were analyzed. Results: The patient had severe BLTS and carried a novel missense variant c.632A>G (p.N211S) in NKX2-1, which failed to bind to specific DNA promoters, reducing their transactivation. TAZ cotransfection did not significantly increase transcription of these genes, although the variant retained its ability to bind to TAZ. Conclusions: We identify a novel pathogenic NKX2-1 variant that causes severe BLTS and is inherited through germline mosaicism. The mutant lacks DNA-binding capacity, impairing transactivation and suggesting that NKX2-1 binding to DNA is essential for TAZ-mediated transcriptional rescue.

Differential diagnosis of Huntington's disease- neurological aspects of NKX2-1-related disorders

Benign hereditary chorea (BHC) is an inherited neurological disorder consisting of childhood-onset, nonprogressive chorea, generally without any other manifestations. In most reported cases, the inheritance of BHC is autosomal dominant but both incomplete penetrance and variable expressivity are observed and can be caused by NKX2-1 mutations. The spectrum contains choreoathetosis, congenital hypothyroidism, and neonatal respiratory distress syndrome. The neurological symptoms can be misdiagnosed as Huntington's disease (HD). The two Polish families were diagnosed with NKX2-1 gene mutations and a literature review concerning the NKX2-1-related disorders was conducted. All family members were examined by experienced movement disorders specialists. PubMed database was searched to obtain previously described NKX2-1 cases. Whole exome sequencing (WES) was performed in one proband (Family A) and direct NKX2-1 sequencing in the second (Family B). Two Polish families were diagnosed with NKX2-1 gene mutations (p.Trp208Leu and p.Cys117Alafs*8). In one family, the co-occurrence of HD was reported. Forty-nine publications were included in the literature review and symptoms of 195 patients with confirmed NKX2-1 mutation were analyzed. The most common symptoms were chorea and choreiform movements, and delayed motor milestones. The NKX2-1 mutation should always be considered as a potential diagnosis in families with chorea, even with a family history of HD. Lack of chorea does not exclude the NKX2-1-related disorders.

Systematic review of drug therapy for chorea in NXK2-1-related disorders: Efficacy and safety evidence from case studies and series

BACKGROUND

The NKX2-1-related disorders (NKX2-1-RD) is a rare disorder characterized by choreiform movements along with respiratory and endocrine abnormalities. The European Reference Network of Rare Neurological Disorders funded by the European Commission conducted a systematic review to assess drug treatment of chorea in NKX2-1-RD, aiming to provide clinical recommendations for its management.

METHODS

A systematic pairwise review using various databases, including MEDLINE, Embase, Cochrane, CINAHL, and PsycInfo, was conducted. The review included patients diagnosed with chorea and NKX2-1-RD genetic diagnosis, drug therapy as intervention, no comparator, and outcomes of chorea improvement and adverse events. The methodological quality of the studies was assessed, and the study protocol was registered in PROSPERO.

RESULTS

Of the 1417 studies examined, 28 studies met the selection criteria, consisting of 68 patients. The studies reported 22 different treatments for chorea, including carbidopa/levodopa, tetrabenazine, clonazepam, methylphenidate, carbamazepine, topiramate, trihexyphenidyl, haloperidol, propranolol, risperidone, and valproate. No clinical improvements were observed with carbidopa/levodopa, tetrabenazine, or clonazepam, and various adverse effects were reported. However, most patients treated with methylphenidate experienced improvements in chorea and reported only a few negative effects. The quality of evidence was determined to be low.

CONCLUSIONS

The management of chorea in individuals with NKX2-1-RD presents significant heterogeneity and lack of clarity. While the available evidence suggests that methylphenidate may be effective in improving chorea symptoms, the findings should be interpreted with caution due to the limitations of the studies reviewed. Nonetheless, more rigorous and comprehensive studies are necessary to provide sufficient evidence for clinical recommendations.

Altered pituitary morphology as a sign of benign hereditary chorea caused by TITF1/NKX2.1 mutations

Benign hereditary chorea (BHC) is a rare genetically heterogeneous movement disorder, in which conventional neuroimaging has been reported as normal in most cases. Cystic pituitary abnormalities and features of empty sella have been described in only 7 patients with BHC to date. We present 4 patients from 2 families with a BHC phenotype, 3 of whom underwent targeted pituitary MR imaging and genetic testing. All four patients in the two families displayed a classic BHC phenotype. The targeted pituitary MR imaging demonstrated abnormal pituitary sella morphology. Genetic testing was performed in three patients, and showed mutations causing BHC in three of the patients, as well as identifying a novel nonsense mutation of the TITF1/NKX2-1 gene in one of the patients. The presence of the abnormal pituitary sella in two affected members of the same family supports the hypothesis that this sign is a distinct feature of the BHC phenotype spectrum due to mutations in the TITF1 gene. Interestingly, these abnormalities seem to develop in adult life and are progressive. They occur in at least 26% of patients affected with Brain-lung-thyroid syndrome. As a part of the management of these patients we recommend to perform follow-up MRI brain with dedicated pituitary imaging also in adult life as the abnormality can occur years after the onset of chorea.

A Not So Benign Family Pedigree With Hereditary Chorea: A Broader Phenotypic Expression or Additional Picture?

NKX2-1 mutations have been usually associated with a non-progressive neurological disease. Recent reports revealed a vast variability regarding its clinical expressivity. Aim of this work was widening the Benign Hereditary Chorea neurological, cognitive and behavioral phenotype through the description of a child and her family pedigree. Molecular analysis focused on NKX2-1 gene revealed a novel frameshift mutation in the three-generation members described. Cognitive scales detected a relevant developmental delay, and the clinical observation and Autism Diagnostic Observation Schedule -2 administration allowed the diagnosis of autism spectrum disorder in the proband. Microarray testing, further executed to exclude a double hit contextually provoking the complex neurodevelopmental disorder, revealed the 22q11.2 Duplication Syndrome. This paper may contribute to enlarge Benign Hereditary Chorea variable expressivity and, together with other studies reported in the literature, underlines the need to reconsider the term "benign," verifying the opportunity of more a complex diagnosis.

Is Benign Hereditary Chorea Really Benign? Brain-Lung-Thyroid Syndrome Caused by NKX2-1 Mutations

BACKGROUND

Since its localization to the NKX2-1 gene in 2002, the phenotype of the disorder historically called "benign hereditary chorea" has been expanding beyond chorea.

METHODS

The phenomenology of movement disorders and other symptomatology associated with mutations in NKX2-1 were characterized after a detailed evaluation of consecutive patients evaluated in our clinic over the past 3 years.

RESULTS

We studied 5 patients (3 females), ages 2 to 31 years, with confirmed pathogenic variants in NKX2-1. All patients exhibited chorea, gross motor delay, and gait impairment. Other symptoms included neonatal respiratory failure (n = 4), cognitive deficits (n = 3), hypothyroidism (n = 4), joint laxity (n = 2), myoclonus (n = 1), hypotonia (n = 3), and seizures (n = 1). Chorea often proved refractory to medical therapies.

CONCLUSIONS

The phenotype associated with pathogenic variants in NKX2-1 frequently includes disabling and often medically refractory neurological and non-neurological abnormalities. We therefore suggest that the term benign hereditary chorea be abandoned in favor of its genetic designation as NKX2-1-related disorder.