The clinical and genetic spectrum of autosomal-recessive <i>TOR1A</i>-related disorders
Afshin Saffari, Tracy Lau, Homa Tajsharghi, Ehsan Ghayoor Karimiani, Ariana Kariminejad, Stephanie Efthymiou, Giovanni Zifarelli, Tipu Sultan, Mehran Beiraghi Toosi, Sahar Sedighzadeh, Victoria Mok Siu, Juan Darío Ortigoza‐Escobar, Aisha Al‐Shamsi, Shahnaz Ibrahim, Nouriya Al‐Sannaa, Walla Al‐Hertani, Sandra Whalen, Mark A. Tarnopolsky, Shahryar Alavi, Chumei Li, Debra-Lynn Day-Salvatore, Maria Jesús Martínez-González, Kristin M Levandoski, Emma Bedoukian, Suneeta Madan‐Khetarpal, Michaela J. Idleburg, Minal Menezes, Aishwarya Siddharth, Konrad Platzer, Henry Oppermann, Martin Smitka, Felicity Collins, Monkol Lek, Mohmmad Shahrooei, Maryam Ghavideldarestani, Isabella Herman, John Rendu, Julien Fauré, Janice Baker, Vikas Bhambhani, Laurel Calderwood, Javad Akhondian, Shima Imannezhad, Hanieh Sadat Mirzadeh, Narges Hashemi, Mohammad Doosti, Mojtaba Safi, Najmeh Ahangari, Paria Najarzadeh Torbati, Soheila Abedini, Vincenzo Salpietro, Elif Yılmaz Güleç, Safieh Eshaghian, Mohammadreza Ghazavi, Michael T Pascher, Marina Vogel, Angela Abicht, Sébastien Moutton, Ange‐Line Bruel, Claudine Rieubland, Sabina Gallati, Tim M. Strom, Hanns Lochmüller, Mohammad Hasan Mohammadi, Javeria Raza Alvi, Elaine H. Zackai, Beth Keena, Cara Skraban, Seth Berger, E. Hallie Andrew, Elham Rahimian, Michelle M. Morrow, Ingrid M. Wentzensen, Francisca Millan, Lindsay B. Henderson, Hormos Salimi Dafsari, Heinz Jungbluth, Natalia Gomez‐Ospina, Anne McRae, Merlene Peter, Danai Veltra, Nikolaos M. Marinakis, Christalena Sofocleous, Farah Ashrafzadeh, Davut Pehli̇van, Johannes R. Lemke, Judith Melki, A. Bénézit, Peter Bauer, Denisa Weis, James R. Lupski, Jan Senderek, John Christodoulou, Wendy K. Chung, Rose E. Goodchild, Amaka C Offiah, Andrés Moreno-De-Luca, Mohnish Suri, Darius Ebrahimi‐Fakhari, Henry Houlden
Abstract
In the field of rare diseases, progress in molecular diagnostics led to the recognition that variants linked to autosomal-dominant neurodegenerative diseases of later onset can, in the context of biallelic inheritance, cause devastating neurodevelopmental disorders and infantile or childhood-onset neurodegeneration. TOR1A-associated arthrogryposis multiplex congenita 5 (AMC5) is a rare neurodevelopmental disorder arising from biallelic variants in TOR1A, a gene that in the heterozygous state is associated with torsion dystonia-1 (DYT1 or DYT-TOR1A), an early-onset dystonia with reduced penetrance. While 15 individuals with AMC5-TOR1A have been reported (less than 10 in detail), a systematic investigation of the full disease-associated spectrum has not been conducted. Here, we assess the clinical, radiological and molecular characteristics of 57 individuals from 40 families with biallelic variants in TOR1A. Median age at last follow-up was 3 years (0-24 years). Most individuals presented with severe congenital flexion contractures (95%) and variable developmental delay (79%). Motor symptoms were reported in 79% and included lower limb spasticity and pyramidal signs, as well as gait disturbances. Facial dysmorphism was an integral part of the phenotype, with key features being a broad/full nasal tip, narrowing of the forehead and full cheeks. Analysis of disease-associated manifestations delineated a phenotypic spectrum ranging from normal cognition and mild gait disturbance to congenital arthrogryposis, global developmental delay, intellectual disability, absent speech and inability to walk. In a subset, the presentation was consistent with foetal akinesia deformation sequence with severe intrauterine abnormalities. Survival was 71%, with higher mortality in males. Death occurred at a median age of 1.2 months (1 week-9 years), due to respiratory failure, cardiac arrest or sepsis. Analysis of brain MRI studies identified non-specific neuroimaging features, including a hypoplastic corpus callosum (72%), foci of signal abnormality in the subcortical and periventricular white matter (55%), diffuse white matter volume loss (45%), mega cisterna magna (36%) and arachnoid cysts (27%). The molecular spectrum included 22 distinct variants, defining a mutational hotspot in the C-terminal domain of the Torsin-1A protein. Genotype-phenotype analysis revealed an association of missense variants in the 3-helix bundle domain to an attenuated phenotype, while missense variants near the Walker A/B motif as well as biallelic truncating variants were linked to early death. In summary, this systematic cross-sectional analysis of a large cohort of individuals with biallelic TOR1A variants across a wide age-range delineates the clinical and genetic spectrum of TOR1A-related autosomal-recessive disease and highlights potential predictors for disease severity and survival.