Hirayama Disease in A Patient with Loeys-Dietz Syndrome: The First Reported Association.

Introduction: Hirayama disease (HD) is a rare, self-limiting cervical flexion myelopathy causing progressive, painless distal upper-limb weakness, typically in young Asian males. Loeys-Dietz syndrome (LDS) is a heritable connective tissue disorder due to TGF-β pathway variants, associated with dural ectasia. Their co-occurrence has not previously been reported. Case description: We describe a 23-year-old woman with genetically confirmed LDS type 2 who developed progressive, painless distal upper-limb weakness, initially unilateral and later bilateral. Examination and electrophysiology showed a C7-T1 polyradicular pattern. Dynamic flexion cervical magnetic resonance imaging (MRI) demonstrated anterior displacement of the posterior dural sac at C5-C7, fully reversible on extension, confirming HD. Conclusion: This presentation was atypical for HD (female sex, third-decade onset, bilateral course), yet electrophysiological and dynamic-MRI findings were unequivocal. HD should be considered in patients with heritable connective tissue disease presenting with progressive distal upper-limb weakness, irrespective of sex or age, and dynamic flexion MRI is essential for diagnosis. LEARNING POINTS: Hirayama disease should be considered in progressive, painless distal upper-limb weakness even outside its classic demographic (young Asian males), including in women and in patients with an underlying connective tissue disorder.Dynamic (flexion) cervical magnetic resonance imaging is required to demonstrate the anterior dural sac displacement that confirms the diagnosis and avoids unnecessary immunomodulatory treatment.Heritable connective tissue disorders such as Loeys-Dietz syndrome may modify cervical dural biomechanics, and internists should be aware of neuromuscular complications beyond the classical cardiovascular, skeletal and dural manifestations.