Unilateral Tongue Atrophy in SMAD3: A Case Report

Background: Mothers Against Decapentaplegic Homolog 3 (SMAD3) is a disorder of the protein encoded at locus 15q22.33 and involved in the transcription of growth factor-beta (TGF) signalling. In this disorder, SMAD3 encoding is impaired, resulting in a connective tissue disorder with multisystem involvement (Bertoli-Avella et al., 2015; Dulac et al., 2019). This case is the first to describe unilateral tongue atrophy as an initial presentation of SMAD3, thereby providing an important contribution to the literature. Clinical History and Exam: A 43-year-old patient described a 1–2-week history in which he noted that half of his tongue had wasted away, and he had difficulty vocalizing. The patient experienced no pain, dysphagia, focal weakness, shortness of breath, or vision change. However, a right-sided tongue deviation without fasciculations was noted. Neurologic examination revealed unilateral tongue atrophy on the right with loss of furrowing. There was a symmetric pterygoid function, and the uvula was midline. Diagnosis, Interventions, and Outcomes: Considerations included a mass in the oropharynx or brain lesion. Evaluations included an unremarkable computed tomography angiogram of the head and neck. A brain magnetic resonance image demonstrated asymmetry of the palatine tonsil. Flexible fibreoptic laryngoscopy was performed and non-diagnostic. A magnetic resonance angiography of the chest revealed severe aortic dilatation. The genetic evaluation included DNA testing, which was confirmatory for SMAD3. Conclusion: The disorder, SMAD3, should be considered in any patient presenting with unilateral cranial nerve findings, including tongue atrophy and a history of aortic aneurysm. Recognizing that SMAD3 is a diagnostic consideration in patients with unilateral cranial nerve involvement will result in a timely diagnosis and intervention and the ability to screen asymptomatic family members.