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Early Clinical, Imaging, and Pathological Characteristics of SRPK3/TTN-Digenic Myopathy
Journal article   Open access   Peer reviewed

Early Clinical, Imaging, and Pathological Characteristics of SRPK3/TTN-Digenic Myopathy

Rotem Orbach, Sandra Donkervoort, Carola Hedberg-Oldfors, Giovanni Baranello, Dimah Saade, Precilla D'Souza, Ruchee Patel, Eva Michael, A Reghan Foley, Diana Bharucha-Goebel, …
Annals of clinical and translational neurology
05/14/2026
DOI: 10.1002/acn3.70401
PMID: 42135902
url
https://doi.org/10.1002/acn3.70401View
Published (Version of record) Open Access

Abstract

SRPK3/TTN-digenic myopathy was recently established as a skeletal muscle myopathy caused by digenic inheritance. This study characterizes the early clinical presentation of SRPK3/TTN-digenic myopathy in one previously reported and seven newly identified pediatric patients. Next generation sequencing and deep clinical phenotyping provide detailed genetic, clinical, imaging, and histopathological characterization of SRPK3/TTN-digenic myopathy. From the cohort of eight male patients (5-19 years at last evaluation), five presented prenatally with reduced fetal movements. At the time of birth, five had hypotonia, two had contractures, and two had respiratory distress. All patients demonstrated motor delay and muscle weakness within the first 15 months of life. Independent ambulation was achieved in six patients (ages 1.5-4 years); three could run. Variable respiratory compromise was documented as early as 5 years of age, with one patient requiring non-invasive nocturnal ventilation support. Cardiac evaluation was normal in all except one patient who had left ventricular non-compaction cardiomyopathy. Muscle MRI demonstrated mild, slowly progressive fibroadipose replacement of muscle with striking early selective involvement of the semitendinosus muscle. Histopathologic and ultrastructural features mimicked TTN-related myopathy (titinopathy), showing abnormal fiber size variation, increased internally placed nuclei, type 1 fiber predominance, and cores/minicores. This work highlights the early clinical manifestations of SRPK3/TTN-digenic myopathy and demonstrates early muscle imaging patterns and histopathological features that are indistinct from those observed in monogenic biallelic titinopathy cases. These features could help with the potentially challenging interpretation of digenic SRPK3 and TTN variants to allow for a confident clinical diagnosis of this novel congenital myopathy.
titin digenic muscle‐specific protein kinase muscle MRI congenital myopathy

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