Penyakit Wilson

01Pathophysiology

Wilson disease is an autosomal recessive disorder caused by mutations in the ATP7B gene located on chromosome 13. This gene encodes a copper-transporting ATPase expressed predominantly in hepatocytes. Under normal conditions, ATP7B serves two critical functions: it incorporates copper into apoceruloplasmin to form functional ceruloplasmin, and it facilitates the biliary excretion of excess copper. When ATP7B is dysfunctional, both processes fail.

The result is a two-pronged problem. First, because copper cannot be loaded onto apoceruloplasmin, serum ceruloplasmin levels drop. The ceruloplasmin that does circulate is the apoform (copper-free), which is rapidly degraded, further lowering measurable levels. Second, because biliary excretion is impaired, copper progressively accumulates within hepatocytes. Early in the disease, the liver can sequester the excess copper, but once hepatocyte storage capacity is overwhelmed, free (non-ceruloplasmin-bound) copper spills into the bloodstream.

This circulating free copper then deposits in extrahepatic tissues. In the brain, copper accumulates preferentially in the basal ganglia (especially the putamen and globus pallidus), causing oxidative damage and neuronal death. This explains the movement disorders: tremor, dystonia, rigidity, and the characteristic wing-beating tremor. Deposition in the cerebral cortex and brainstem accounts for psychiatric symptoms (depression, psychosis, personality changes) and bulbar signs (dysarthria, dysphagia, drooling).

In the cornea, copper deposits in Descemet's membrane, producing the golden-brown Kayser-Fleischer (KF) rings visible on slit-lamp examination. These rings are present in nearly all patients with neuropsychiatric Wilson disease, though they may be absent in patients presenting with isolated hepatic disease.

In the kidneys, copper deposition can cause renal tubular dysfunction (Fanconi-like syndrome with aminoaciduria, phosphaturia, and uricosuria). In the blood, sudden release of copper from damaged hepatocytes triggers Coombs-negative hemolytic anemia through direct oxidative damage to red blood cell membranes. This hemolytic crisis is frequently the presenting feature in patients with fulminant Wilson disease and is a hallmark exam clue.

02Classification and Clinical Manifestation

Wilson disease presents along a clinical spectrum that can be divided into overlapping phenotypic categories. Most patients present between the ages of 5 and 40, with hepatic disease tending to present earlier and neuropsychiatric disease appearing later.

A critical teaching point: when a vignette describes a teenager or young adult with unexplained liver disease plus any neuropsychiatric symptom, Wilson disease should be at the top of the differential. The combination of organ systems involved is the primary clue.

03Diagnostic Workup

The diagnostic approach begins with serum ceruloplasmin, which serves as the best initial screening test. A level below 20 mg/dL raises suspicion, but this test alone is neither sensitive nor fully reliable. Ceruloplasmin is an acute-phase reactant, so inflammation, estrogen states (pregnancy, oral contraceptives), and hepatic synthetic dysfunction can all produce misleading values. Low ceruloplasmin is also seen in other conditions such as nephrotic syndrome, protein-losing enteropathy, and Menkes disease.

Every patient with suspected Wilson disease should undergo a slit-lamp examination by an ophthalmologist to look for Kayser-Fleischer rings. While nearly universal in neurologic Wilson disease, KF rings are absent in roughly half of patients presenting with hepatic disease alone, so their absence does not exclude the diagnosis.

The next step is a 24-hour urine copper collection, which quantifies copper excretion. Values exceeding 100 micrograms per day are strongly supportive. In equivocal cases, a D-penicillamine challenge test (measuring urine copper after administering penicillamine) can be performed, particularly in pediatric patients.

The gold standard and most accurate test is liver biopsy with quantitative hepatic copper measurement. A value exceeding 250 micrograms per gram of dry weight is diagnostic. Liver biopsy also allows histologic assessment of the degree of fibrosis or cirrhosis.

Genetic testing for ATP7B mutations is useful for confirming ambiguous cases and is essential for screening first-degree relatives of a confirmed patient. Over 500 mutations have been identified, so full gene sequencing is typically required.

 Brain MRI is indicated when neuropsychiatric symptoms are present. Classic findings include bilateral T2 hyperintensity in the basal ganglia (putamen, caudate, thalamus). The "face of the giant panda" sign, a pattern of signal changes in the midbrain tegmentum, is a frequently tested radiologic finding.

 A key exam pearl: in fulminant Wilson disease, the alkaline phosphatase is often disproportionately low (sometimes even normal) despite severe liver injury, and the AST-to-ALT ratio is typically greater than 2. An alkaline phosphatase-to-total bilirubin ratio below 4 and an AST-to-ALT ratio above 2.2 strongly suggest Wilsonian fulminant liver failure and help distinguish it from other causes.

04Management and Treatment

Acute stabilization in symptomatic Wilson disease begins with copper chelation therapy. D-penicillamine is the classic first-line chelator. It works by binding free copper in the blood and promoting its urinary excretion. Dosing starts low (250 mg/day) and is gradually increased over weeks to a target of 1,000 to 1,500 mg/day, divided into 2 to 4 doses taken on an empty stomach. Pyridoxine (25 mg/day) is supplemented because penicillamine is a pyridoxine antagonist. Patients must be monitored closely for adverse effects including bone marrow suppression (leukopenia, thrombocytopenia), nephrotoxicity (proteinuria, nephrotic syndrome), lupus-like syndrome, and elastosis. About 30% of patients with neurologic Wilson disease experience initial neurologic worsening upon starting penicillamine, which is an important exam concept.

Trientine is the preferred alternative when penicillamine is not tolerated. It has a similar mechanism of action (copper chelation and urinary excretion) but a more favorable side effect profile. Dosing is 750 to 1,500 mg/day in divided doses on an empty stomach.

For maintenance therapy after initial decoppering, or for presymptomatic patients identified through family screening, zinc acetate is the treatment of choice. Zinc works by a different mechanism: it induces metallothionein in enterocytes, which binds dietary copper in the gut and prevents its absorption. When these copper-loaded enterocytes are shed during normal mucosal turnover, the trapped copper is excreted in feces. Zinc is dosed at 50 mg of elemental zinc three times daily, taken between meals. It should not be taken simultaneously with chelators because zinc can chelate the chelator itself and reduce its efficacy; a separation of at least 1 hour is recommended if both are used during the transition period.

Liver transplantation is the definitive treatment for fulminant Wilson disease and for patients with decompensated cirrhosis who do not respond to medical therapy. Transplantation is curative because the donor liver expresses functional ATP7B, correcting the underlying metabolic defect. Following transplant, chelation therapy is no longer needed.

Dietary restriction of high-copper foods (shellfish, organ meats, chocolate, nuts, mushrooms) is recommended as an adjunct but is never sufficient as standalone treatment.

Treatment is lifelong. Abrupt discontinuation of chelation or zinc therapy can precipitate acute decompensation and fulminant liver failure, even in patients who have been stable for years. This is a commonly tested pitfall.

05Differential Diagnosis and Distractors

The most common source of confusion is between Wilson disease and autoimmune hepatitis, as both affect young patients and cause chronic liver disease. The distinguishing features are the KF rings, low ceruloplasmin, and Coombs-negative hemolytic anemia in Wilson versus autoantibodies and Coombs-positive hemolysis in autoimmune hepatitis.

Menkes disease is a frequently tested comparison because both conditions involve ceruloplasmin and copper metabolism. The critical difference is that Menkes is an absorption defect (X-linked, copper cannot be absorbed from the gut, so serum copper is low), whereas Wilson is an excretion defect (autosomal recessive, copper cannot be excreted, so tissue copper is high).

06Traps and High-Yield Pearls

The most common way students get questions on Wilson disease wrong is by failing to recognize the atypical or isolated presentations. A vignette may describe a teenager with only psychiatric symptoms and no overt liver disease, or a child with Coombs-negative hemolytic anemia and mildly abnormal liver tests. In both scenarios, Wilson disease must be considered.

Another frequent trap is the fulminant liver failure presentation: when a young patient presents with acute liver failure, a disproportionately low alkaline phosphatase, and an AST-to-ALT ratio greater than 2, Wilson disease is the answer, and the next best step is emergent evaluation for liver transplantation, not chelation therapy alone, because chelation cannot reverse fulminant hepatic necrosis fast enough.

Students also confuse the direction of copper changes. Remember: serum ceruloplasmin is low, total serum copper is low (because most serum copper is bound to ceruloplasmin, which is depleted), but free serum copper is high, urine copper is high, and hepatic copper is high. The distinction between total and free copper is a classic source of incorrect answers.

Finally, do not forget the initial neurologic worsening with D-penicillamine. A vignette describing a Wilson disease patient whose tremor worsens after starting chelation is not a treatment failure; it is the expected phenomenon of copper mobilization. The tested concept here is knowing that trientine is the preferred alternative for neurologic Wilson disease to avoid this complication, and that some experts now advocate trientine as first-line therapy for neurologic presentations altogether.