Potential of the international scoring system for the diagnosis of Wilson disease to differentiate Japanese patients who need anti-copper treatment

Aim: Patients with Wilson disease show complex clinical features. Accurate diagnosis at the initial clinical manifestation is important for patients to receive effective treatment with anti-copper agents. In this study, we assessed whether the international scoring system for the diagnosis of Wilson disease is a reliable tool for screening Japanese patients with primary copper toxicosis requiring anti-copper treatment. Methods: Twenty-three Japanese patients suspected of Wilson disease were enrolled in this study. We performed long-range polymerase chain reaction to detect ATP7B mutations in this series. Finally, we retrospectively assessed the reliability of using a diagnostic score of 4 or more points as the cut-off for this scoring system. Results: Ten patients were homozygous or compound heterozygous for ATP7B mutations including a novel mutation of 3837bp deletion including 3 exons. The mutation would have been missed by the traditional analysis. Six patients were heterozygous for ATP7B mutations. Three of these six patients had additional diagnostic points. The other three patients were diagnosed as carriers of a mutant gene based on their low scores. One of the seven patients free from ATP7B mutation was affected by copper toxicosis. Though the score was 3 points based on increased urinary copper and copper-positive cirrhosis, anti-copper treatment promptly improved liver failure, which was likely due to idiopathic copper toxicosis. Conclusion: The international scoring system for diagnosis of Wilson disease is a fairly reliable tool for screening Japanese patients who need anti-copper treatment. Caution is needed for patients with possible idiopathic copper toxicosis because the maximal score is 4 points.