Increased soft tissue in the posterior cervical and upper back area of patients on HIV-1 protease inhibitors

Background: Corticosteroids as well as sex hormones affect the redistribution of subcutaneous fat and the percentage of lean body mass. In addition, some stromal cells express steroid receptors, and the quantity and distribution of these receptors vary at different body sites and between sexes. Inhibitors of HIV-1 protease may affect steroid hormone metabolism through their effect on cytochrome P450. Objectives: To determine the changes in the tissue of the back in three HIV-1+ patients who developed increased soft tissue in posterior cervical and upper back areas while on HIV-1 protease inhibitors. Methods: Punch biopsies of the involved posterior cervical and upper back areas were done. These included subcutaneous adipose tissue. Routine hematoxylin and eosin-stained sections, along with special stains for elastic and stromal mucin, and immunohistochemical stains for CD34 (HPCA-1 and Factor XIIIa) were evaluated. Results: Histologically all three patients showed identical features. There was expansion of the dermis with decreased periadnexal fat and marked widening of the fibrous septa within the expanded subcutaneous fat. Conclusions: The posterior cervical and upper back area appears to be a common site for localization of mesenchymal tumours that show some fat differentiation and produce an increase in stromal matrix material. Mesenchymal cell populations within this area are also affected by systemic diseases. A male predominance pattern occurs with these conditions, and steroid receptors are expressed on some mesenchymal cells, that vary with the body location. Thus, this observation may be related to the effects of protease inhibitors on steroid hormone metabolism through their inhibition of cytochrome P-450.