An Unexpected Smile: risus sardonicus and wing-beating tremor in a first office visit

Context: We present a noteworthy reminder of Wilson disease’s classical manifestations, which may become rarer in clinical practice as availability of genetic tests increases, allowing timely diagnosis and treatment. Case report: A 29 year-old woman developed progressive and asymmetric upper limb tremor and dystonia over 1 year, along with speech and feeding impairment in the last two weeks. Examination revealed segmental dystonia with risus sardonicus, open-jaw oromandibular and severe left arm dystonia, along with wing-beating tremor. Bilateral Kayser-Fleischer ring, low serum ceruloplasmin level, high urinary copper level, bilateral putaminal lesions on brain MRI and detection of ATP7B mutation confirmed Wilson disease (WD). A nasoenteric tube was inserted and D-penicillamine was started. Conclusion: This case illustrates the hallmark neuro-ophtalmological signs of WD: wing-beating tremor, risus sardonicus and Kayser-Fleischer ring. The former is probably associated with lesions in the dentato-rubro-thalamic pathway¹ and means a low frequency, high amplitude, posture-induced proximal arm tremor. Risus sardonicus means a fixed smile due to risorius muscle dystonia². Although it is a well-known manifestation of cephalic tetanus, it is also frequent in WD¹. Finally, the Kayser-Fleischer ring is caused by copper accumulation in the Descemet membrane and occurs in almost 100% of patients with neurological WD².