More severe parenchymal injury in chronic hepatitis C acquired by recent injection drug use

Histologic liver injury is reported to be less severe in persons who acquire hepatitis C through injection drug use (IDU) than by blood transfusion. Because age correlates with histologic severity, it may be that differences between routes of acquisition reflect the younger age of most drug abusers. The early histopathologic changes of hepatitis C acquired through IDU are less defined, probably because of the lack of liver biopsy material from a cohort of patients not long after initial exposure. The availability of material from a cohort of patients who had liver biopsy for IDU-related hepatitis C in the 1970s enabled us to compare the histology with that of current patients.

Liver biopsies of a group of injection drug users (n=70, all males; mean age, 27.6 years, designated as Group 1) in the 1970s cohort were compared with biopsies of patients (n=63, all males; mean age, 48 years, designated as Group 2, 23 who admitted past IDU) entering a treatment trial in 1999. All patients were positive for anti-HCV at the time of biopsy.

The histologic features of the 23 patients in Group 2 with a history of IDU did not differ significantly from the other 40 patients who denied past IDU. Using a modified Histologic Activity Index (HAI), there was no difference between Group 1 and Group 2 in portal inflammation or periportal injury. However, parenchymal (lobular) injury and inflammation was significantly (P<0.0001) greater in Group 1 than Group 2. Fibrosis was significantly (P=0.014) greater in Group 2.

The degree of parenchymal injury was greater in Group 1 than Group 2, perhaps because they were closer to the time of exposure or possibly because of a stronger immunologic response in younger patients. The degree of hepatic fibrosis was greater in Group 2, suggesting that progression with age may be the natural history of chronic hepatitis C.