Case report: Huppke–Brendel syndrome in an adult, mistaken for and treated as Wilson disease for 25 years

BACKGROUND: Huppke–Brendel (HB) syndrome is an autosomal recessive disease caused by variants in the SLC33A1 gene. Since 2012, less than ten patients have been reported, none survived year six. With neurologic involvement and ceruloplasmin deficiency, it may mimic Wilson disease (WD). OBJECTIVES AND METHODS: We report the first adult patient with HB. RESULTS: The patient suffered from moderate intellectual disability, partial hearing loss, spastic ataxia, hypotonia, and unilateral tremor of parkinsonian type. At age 29, she was diagnosed with WD based on neurology, elevated 24H urinary copper, low ceruloplasmin, and pathological (65)Cu test. Approximately 25 years later, genetic testing did not support WD or aceruloplasminemia. Full genome sequencing revealed two likely pathogenic variants in SLC33A1 which combined with re-evaluation of neurologic symptoms and MRI suggested the diagnosis of HB. CONCLUSION: Adult patients with HB exist and may be confused with WD. Low ceruloplasmin and the absence of ATP7B variants should raise suspicion.