The authors describe two boys, monozygotic twins, with Wilson’s disease manifested by atypical initial symptoms. Twin A met according to the diagnostic scoring system the criteria for the probable diagnosis of autoimmune hepatitis. The controversial response to immunosupressive treatment stimulated the application of the penicillinamine test and examination of the copper content in hepatic tissue. This examination confirmed the diagnosis of Wilson’s disease. In twin B the first clinical symptom was arthritis of the knee joint on account of which he was treated with sulfasalazine. Establishment of the correct diagnosis in this patient was based on the positive result of examinations made in twin A. The authors draw attention to the fact that it is necessary to take Wilson’s disease into consideration in particular in adolescent patients with an obscure hepatopathy even when the ceruloplasmin and serum copper levels are normal or marginal, when the urinary 24-hour copper excretion is normal and the Kayser-Fleischer ring is absent. In addition to the penicillinamine test and assessment of copper in the liver the diagnosis of Wilson’s disease can be made by direct DNA analysis. The sensitivity of the method is however limited due to the large number of known mutations.

        Key words: Wilson’s disease, monozygotic twins, DNA analysis