Hypermetabolic subcutaneous fat in patients on highly active anti-retroviral therapy treatment: Subtle finding with implications.

Lipodystrophy (LD) is a serious complication of highly active anti-retroviral therapy, characterized by peripheral fat wasting, central adiposity and metabolic changes. Since the disfiguration caused by LD is permanent, the focus of management is on early detection to arrest progression. We report a case where ancillary finding of increased fluorine-18 fluoro-2-deoxyglucose (F-18 FDG) uptake in the sub-cutaneous fat helped early detection of LD and led to early intervention to arrest progression. Though F-18 FDG positron emission tomography/computed tomography scan is not recommended to diagnose LD, conscious reporting of this finding when present can greatly influence patient management.

INTRODUCTION

Lipodystrophy (LD) is a serious complication of highly active anti-retroviral therapy (HAART) and is associated with increased fluoro-2-deoxyglucose (FDG) uptake. Conscious reporting of this ancillary finding may help early identification and intervention to arrest the progression of this serious metabolic disorder.

CASE REPORT

A 34-year-old gentleman, on anti-retroviral therapy since 3 years was treated for lymphoblastic lymphoma. He was referred for fluorine-18 FDG positron emission tomography/computed tomography (PET/CT) study for follow-up evaluation. The scan revealed hypermetabolism in the mid thorax corresponding to esophageal candidiasis [Figure 1]. With a history of HAART therapy of 3 years duration, the scintigraphic findings of increased FDG uptake in the subcutaneous adipose tissue was suggestive of LD. He was treated with antifungal medications. To arrest the progression of LD, stavudine was replaced by tenofovir and diet modification was advised.

Figure 1

Maximum intensity projected image (a) revealed increased linear FDG uptake in the mid thorax and diffuse low grade FDG uptake throughout the body. The diffuse low grade FDG uptake on transaxial PET image at infra axillary level (arrows in Figure b) corresponded to the subcutaneous adipose tissue on correlative CT image (arrows in Figure c). The increased focal FDG uptake on the transaxial PET image in the mid thorax at subcarinal level (arrows in Figure d) corresponded to the oesophagus on correlative CT image (arrows in Figure e)

DISCUSSION

HAART has increased the life expectancy and also improved the quality of life of people suffering from human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome. LD is a late but serious complication of HAART caused by mitochondrial damage of adipocytes and characterized by peripheral fat wasting (lipo-atrophy), central adiposity (lipo-hypertrophy), and metabolic changes, such as hyperlipidemia, hyperglycemia, and insulin resistance. Its incidence is related to the dosage and duration of exposure to anti-retrovirals.[123] Its’ prevalence in developing countries, which continue to use older, less expensive antiretroviral drugs, may be as high as 47% after 2 years of therapy.[4] Diagnosis based on anthropometric and biochemical measurements can be made only in the late stages of disease when the disfigurement is largely permanent. Replacement of the offending drug by a less LD-inducing drug in the early stages of disease may arrest its progression.[56] Hence, early detection to arrest progression is of paramount importance.[1] FDG PET/CT study has evolved not only as a tool to improve our understanding of the pathogenesis of HIV-1 infection, but also in diagnosis, staging, restaging, and monitoring therapeutic response in the opportunistic infections and malignancies.[2789101112] Furthermore, increased FDG uptake in subcutaneous adipose tissue has been demonstrated in diagnosed cases of LD.[213] The awareness of this uptake pattern is important when evaluating FDG PET in patients undergoing HAART.