Introduction
New terminology proposed by Tatsumi et al.1 may facilitate a better understanding of the primary copper toxicosis of Wilson’s disease (WD) and a simple approach to diagnose asymptomatic liver damage in the early stage of WD. The classical form is a primary copper-induced liver disease, which may be complicated by lenticular degeneration at a later stage, and which was initially described by SAK Wilson in 1912.1–3 In addition to increased hepatic copper of 250 μg/g dry liver or more, two mutant alleles in the ATP7B gene and reduced serum levels of ceruloplasmin (CP) are found in typical cases.1,3 Other subtype tests include detection of Kayser Fleischer rings, neuropsychiatric signs, and Coombs-negative hemolytic anemia.1,3 The severe hepatic form is another copper-induced liver disease, the former name of which was idiopathic copper toxicosis, proposed by Scheinberg and Sternlieb in 1994.1,4–6 There are currently no tests for the severe hepatic form, other than detection of increased hepatic copper and urinary copper secretion,1,6 and the new subtype tests proposed by Tatsumi et al.1 are combined results of normal CP levels and no mutations in ATP7B.
Another recommendation that Tatsumi et al.1 propose is a treatment for the copper toxicosis of WD. Every patient with WD should receive a short-term treatment trial involving anti-copper regimens, followed by life-long maintenance treatment. For the former, a poor response to anti-copper regimens indicates non-WD. Some patients with WD, especially the severe hepatic form, suddenly present with hepatic failure and require a liver transplantation without the liver biopsy essential for diagnosing WD. In such cases, the postoperative diagnosis of WD should be confirmed by the increased copper content of the removed liver.
It is now an urgent task to establish liver tests for patients with asymptomatic liver damage of WD. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) are favorable liver tests, but they are hampered by the following problems in WD patients: (1) rapid falls of AST and ALT during Coombs-negative hemolytic anemia;7 (2) natural courses of the first increasing and second decreasing stages of AST and ALT;8 and (3) AST having an erythrocyte fraction in WD, where it is significantly affected by copper-induced hemolysis.7,9 When the serum levels of AST and ALT are introduced as tests for the primary liver damage of WD, all problems should be overcome to minimize misdiagnosis.
In this study, we evaluated the potential of serum levels of ALT as representative of age-dependent liver disease activity of WD and determined the optimal age for the ALT test in WD patients.
Methods
Patients
International proposals were used for the diagnosis of WD, with minor modifications.3 The original scoring system for the diagnosis consists of Kayser-Fleischer rings (2 points), neuropsychiatric symptoms (2), Coombs-negative hemolytic anemia (1), urinary copper (max. increase: 2), hepatic copper quantitative (max. increase: 2), serum CP level (max. decrease: 2),10 and ATP7B mutation (2 alleles: 4, one allele: 1). Diagnostic WD is assigned with a score of 4 or more points. Probable WD is assigned with score of 2–3 points. Unlikely WD is assigned with score of 0–1 points. In the patients saved by liver transplantation, the copper content of the removed liver should receive a maximum of 2 points (>250 μg/g dry liver weight). In patients with 2–3 points (probable WD), the diagnosis was retrospectively confirmed by giving an additional 2 points for a good response to anti-copper regimens. A removed liver with copper less than 250 μg/g dry liver and a poor response to anti-copper regimens were set as exclusion criteria. WD cases complicated with either chronic cholestasis or other chronic liver disease, including chronic viral hepatitis, nonalcoholic steatohepatitis, etc., were also excluded from the study.
A total of 52 patients with primary copper toxicosis of WD were enrolled in the study. Forty-five Japanese patients were selected from the databases of three institutes (Aichi Gakuin University School of Pharmacy, Kainan Hospital, and Saiseikai Yokohama Toub Hospital), and 7 infant patients were cited based on a literature review of PubMed to identify relevant papers written in English since 1993.11–16 Clinical data of two Japanese patients were analyzed twice because they were followed for years without anti-copper regimens.
Based on ATP7B analysis and serum levels of CP, the primary copper toxicosis of WD in the studied patients was subtyped into two forms — classical and severe hepatic WD (Table 1).1 Forty-five patients had typical features of the classical form, with two mutant alleles in ATP7B and low levels of serum CP (<20 mg/dL); two other patients had the severe hepatic form, with no mutation in ATP7B and normal levels of serum CP. Five patients had atypical classical forms, with one mutant allele of ATP7B.
Table 1.Fifty-two patients with WD and their subtypes using ATP7B analysis and serum CP levels
| Group of patients | ATP7B | Serum CP (>20 mg/dL) | Patient number | Major subtype |
| Literature, n = 7 | Two mutant alleles | Low | 7 | Classical |
| | Normal | 0 | Classical |
| Patient databases, n = 45 | Two mutant alleles | Low | 38 | Classical |
| | Normal | 1 | Classical |
| One mutant allele | Low | 4 | Classical |
| | Normal | 0 | ? |
| No mutant allele | Low | 0 | ? |
| | Normal | 2 | Severe hepatic |
Methods
The study protocol was approved by the ethics committees of 3 institutes (Aichi Gakuin University School of Pharmacy, Kainan Hospital, and Saiseikai Yokohama Toub Hospital). Serum levels of ALT were determined by one point at entry in all patients with WD, except for those with Coombs-negative hemolytic anemia and complicated acute diseases. The baseline ALT levels of hemolysis patients were obtained at the stage of pre-hemolytic anemia or recovery from anemia.7 In the patients whose WD was found after acute diseases, such as fever episodes and gastrointestinal problems, the baseline ALT was obtained at the recovery stage. Using the serum levels of ALT and onset ages of 52 patients aged between 0.7 and 47 years, a virtual image was made for the natural course of WD. The diagnostic potential of the age-dependent ALT levels was assessed for the primary liver damage of WD.
Results
Virtual images of the natural course of WD using serum ALT levels representative of primary liver disease activities and entry ages of patients are presented in Fig. 1. There are three ALT stages associated with the onset ages of patients. In the first stage, some infants younger than 4 years-old showed low ALT levels. In the second stage, all of the 10 children aged between 4 and 8 years showed high ALT levels (>150 IU/L). In the third stage, patients over the age of 9 years showed a wide range of ALT levels; fifteen of thirty-five patients showed pathologically high ALT levels, while 20 patients had levels that were near-normal. Especially, all seven patients aged 35 years or older showed ALT levels below 50 IU/L.
Discussion
Our observations strongly suggest that a standard liver test — ALT — has the potential to detect most WD patients between the ages of 4 and 8 years-old. Serum ALT levels higher than 150 IU/L are representative of active chronic hepatitis of WD.17,18 Underlying mechanisms of the low ALT levels are different in the first and third stages. The former means that there is no active liver damage in some patients as yet, due to a small amount of toxic copper in the liver,8 while the latter involves silent cirrhosis in some patients. It is well known that, in chronic viral hepatitis, histological progression from chronic hepatitis to cirrhosis is associated with declining inflammation in the liver. Such transformation is of special importance in WD. A large amount of copper is mostly stored in hepatocyte lysosomes of cirrhosis as detoxified cuprothioneins.19,20 Age-dependent copper accumulation in the central nervous system is also associated with silent cirrhosis formation in classical WD.8 As a result, ALT tests partially lose the potential to detect copper-induced liver diseases in patients over 9 years-old.
Based on the natural disease course presented in this study, we can postulate that most patients aged over 9 years had asymptomatically experienced the high ALT stage when between the ages of 4 and 8 years-old. Therefore, children aged between 4 and 8 years may be suitable candidates for special intervention to detect asymptomatic but biochemically active liver damage of WD, as summarized in Table 2.
Table 2.Recommended diagnostic approach to the primary liver disorders of WD
| | WD |
| Classical Form | Severe Hepatic Form |
| 1 | Liver test | Serum ALT test: > 150 IU/L in children aged 4 – 8 yrs |
| 2 | Copper tests | Hepatic copper more than 250 μg/g dry liver |
| | Increased urinary copper secretion (basic and post-penicillamine) |
| 3 | Subtype tests | Hypoceruloplasminemia | Normoceruloplasminemia and no ATP7B mutation |
| | Mutations in ATP7B |
| 4 | Anti-copper tests | Good responses on ALT reduction |
Increased hepatic copper and urinary copper secretion are reliable tests for the copper toxicosis of WD favored by the international proposal.3 Hypoceruloplasminemia1,10 and ATP7B mutations1,3 strongly support the classical form. In contrast, their respective absence does not exclude WD; the negative combination of the two major subtyping tests for the classical form may be transient subtype tests for the severe hepatic form that has no definitive subtype tests, including gene analysis.1,6
A final diagnosis of WD should be confirmed in all children with WD, by anti-copper regimens. A recent study on young patients under 10 years of age revealed that zinc monotherapy reduced serum ALT levels ranging from 243 ± 151 to 70 ± 29 IU/L in 1 month.23 It is also important that copper-overload conditions secondary to chronic cholestasis24 or chronic liver diseases other than WD25,26 could be differentiated by the short-term treatment test.
Because neuropsychiatric symptoms of classical WD appear at a late cirrhotic stage associated with low ALT levels,8 an intentional ALT test for children at the high ALT stage is prophylactic for neuropsychiatric complications. A smaller number of children with WD may have been affected by Coombs-negative hemolytic anemia before such a scheduled ALT test.8 A similar episode in a 7-year-old girl among the 10 patients in the high ALT stage was self-limiting, and she recovered from anemia without any sequelae. ALT intervention specialized to detect asymptomatic WD should be confirmed in a large number of patients.
Conclusions
There are two subtypes of classical and severe hepatic forms in the primary copper toxicosis of WD. A standard liver test of ALT is highly recommended for children between the ages of 4 and 8 years-old to detect asymptomatic WD. The selection criterion is a serum ALT level over 150 IU/L. Increased hepatic copper is an etiological test. Serum CP level and ATP7B analyses are subtype tests. A marked reduction of ALT with anti-copper regimens is diagnostic for WD.
Abbreviations
- ALT:
alanine aminotransferase
- AST:
aspartate aminotransferase
- CP:
ceruloplasmin
- WD:
Wilson’s disease
Declarations
Conflict of interest
The authors have no conflict of interests related to this publication.
Authors’ contributions
Conception of study objective and design (HH, AI, TF), collection of patient data (KW, AO, KK), gene analysis (AK, YT).