HIV

Diagnosis

HIV

History

Eight year old African girl with generalized adenopathy.

Findings

Multiple FDG-avid lymph nodes involving neck, axillae, mediastinum, retroperitoneum, iliac axis, inguinal regions, popliteal fossa and epitrochlear regions. Distribution is symmetrical. The majority of lymph nodes are smaller than 15 mm. Larger inguinal lymph nodes are found (20 mm). SUV max varies between 4 and 8. Spleen is mildly active but of normal size.

DDx

Infectious diseases

Lymphoma

Castleman’s disease

Lupus

Discussion

There was 32 million people living with HIV infection in 2011. HIV infects primarily CD4 T cells. When those cells decline, cell-mediated immunity is weakened and risk of opportunistic infections as well as malignancy increases.

Many studies have demonstrated that HIV viremia is associated with accelerated turnover lymphocytes. This turnover is thought to be the result of proliferation of both HIV-infected cells and uninfected cells. When activated, lymphocytes increase their glucose consumption 20-fold over a short period of time, using aerobic glycolysis.Peripheral generalized lymphadenopathies precede tissue involution and loss of superficial lymph nodes in later disease.

The use of FDG PET in HIV patients has been reported in several occasions.

Scharko et al. observed distinct lymphoid tissue activation in the head and neck during acute disease, a generalized pattern of peripheral lymph nodes activation at mid stage, and involvement of abdominal lymph nodes during late disease, suggesting that lymphoid tissues are engaged in a predictable sequence.

Brust et al. reported that healthy HIV-infected patients with suppressed viral loads and HIV negative individuals have no or little FDG nodal accumulation or any other hypermetabolic areas, whereas viremic individuals with early or advanced HIV had increased FDG in the peripheral nodes. Those findings suggest that FDG has the potential to identify areas of HIV replication.

Since HIV is associated with many infections and malignancies, FDG PET/CT interpretation needs a careful evaluation. Knowing the viral load is paramount. To avoid false positive findings, viral load should be suppressed during a malignancy assessment on FDG PET/CT.

Mhlanga et al. showed in another study that symmetry of nodal uptake appeared to be a valuable tool for differentiating lymphoma from reactive adenopathies in HIV-infected patients and has more discriminating power in aviremic patients.

References

 Lyengar et al : Anatomical loci of HIV-associated immune activation and association with viraemia. Lancet. 2003 Sep 20;362(9388):945-50

 Scharko et al : Whole-body positron emission tomography in patients with HIV-1 infection. Lancet. 2003 Sep 20;362(9388):959-61

Brust et al : Fluorodeoxyglucose imaging in healthy subjects with HIV infection: impact of disease stage and therapy on pattern of nodal activation. AIDS. 2006 Feb 28;20(4):495-503

Goshen et al : PET/CT in the evaluation of lymphoma in patients with HIV-1 with suppressed viral loads. Clin Nucl Med. 2008 Sep;33(9):610-4

Lederman et al : The lymph node in HIV pathogenesis. Semin Immunol. 2008 Jun;20(3):187-95

Lucignani et al : FDG-PET imaging in HIV-infected subjects: relation with therapy and immunovirological variables. Eur J Nucl Med Mol Imaging. 2009 Apr;36(4):640-7

Sathekge et al : Positron emission tomography in patients suffering from HIV-1 infection. Eur J Nucl Med Mol Imaging. 2009 Jul;36(7):1176-84

Sathekge et al : Fluorodeoxyglucose uptake by lymph nodes of HIV patients is inversely related to CD4 cell count.  Nucl Med Commun. 2010 Feb;31(2):137-40

Davison et al : FDG PET/CT in patients with HIV. AJR Am J Roentgenol. 2011 Aug;197(2):284-94

Sathekge et al : FDG-PET imaging in HIV infection and tuberculosis. Semin Nucl Med. 2013 Sep;43(5):349-66

Mhlanga et al : Differentiation of HIV-associated lymphoma from HIV-associated reactive adenopathy using quantitative FDG PET and symmetry. Eur J Nucl Med Mol Imaging. 2014 Apr;41(4):596-604