Objective: To report a patient with a congenital extrahepatic portosystemic shunt with features mimicking those seen in Wilson’s disease

Background: Wilson’s disease is an autosomal recessive disorder caused by pathogenic variants in ATP7B leading to impaired copper transport and accumulation. Rare treatable conditions can mimic aspects of Wilson’s disease

Method: Investigations were undertaken of a 24 year old male with symmetrical upper limb action tremor and low serum caeruloplasmin

Results: Investigations revealed low serum caeruloplasmin, copper, and abnormal liver function tests (elevated ALT, ALP and bilirubin). MRI head showed bilateral T2/FLAIR hyperintensities in the globus pallidus, substantia nigra and cerebellar dentate nuclei. 24 hour urinary copper excretion was normal and Kayser-Fleischer rings were not present. Genetic testing identified a heterozygous pathogenic ATP7B variant (p.His1069Gln). Liver biopsy showed mild fibrosis and normal hepatic copper concentration. The patient was monitored without chelation therapy. The tremor became more disabling and therefore, a Cu-65 incorporation test was performed which showed findings consistent with those seen in Wilson’s disease. Thus on the basis of the neurological and biochemical findings, treatment with penicillamine was started on the assumption that there was a second not yet identified pathogenic variant in the ATP7B gene. His clinical condition remained stable initially and there was an improvement in his liver function tests. Re-evaluation several years after the patient developed self-limiting encephalopathy revealed severe and persistent hyperammonaemia with no cirrhosis. A triple-phase CT scan demonstrated a congenital extrahepatic portosystemic shunt. Penicillamine was discontinued and ammonia scavengers were started, but despite these measures he developed progressive lower limb pyramidal signs. Surgical shunt repair was unsuccessful and he is awaiting a liver transplant.

Conclusion: Congenital portosystemic shunts may produce neurological, biochemical and radiological findings overlapping with those seen in Wilson’s disease. In this case diversion of porto-mesenteric blood into the systemic circulation is postulated to have resulted in a false-positive copper isotope incorporation test. They should be considered in patients with atypical Wilson-like presentations, particularly in the absence of biallelic ATP7B mutations and unexplained hyperammonaemia without cirrhosis.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/congenital-portosystemic-shunting-a-wilsons-disease-mimic/