HISTORY: A 48-year-old patient with Crohn's disease was admitted to our hospital 
with fatigue, icterus, hepatosplenomegaly and ascites. INVESTIGARTIOS: The whole 
blood count revealed a pancytopenia, hyperbilirubinemia and slightly elevated 
transaminases. Examination of the liver histology showed areas of enlarged 
hyperplastic hepatocytes adjacent to areas of atrophic hepatocytes and dilated 
sinusoids.
DIAGNOSIS, TREATMENT AND COURSE: Pancytopenia was most likely 
azathioprine-related. Analysis of the liver histology was highly suggestive of 
an azathioprine-related, nodular regenerative hyperplasia (NRH). After 
discontinuation of azathioprine the patient's condition improved substantially.
CONCLUSIONS: NRH is a rare but potentially serious complication of azathioprine 
therapy. Other causes include various rheumatological, vascular and 
myeloproliferative diseases. When azathioprine is prescribed it must be borne in 
mind that it can cause NRH as a potential adverse effect, and liver enzymes 
should be measured at regular follow-up examinations.