FDG PET Scanning in Hemophagocytic Lymphohistiocytosis

Abstract

Hemophagocytic Lymphohistiocytosis (HLH) is a rare disorder. It progresses rapidly and can be life-threatening. Prompt initiation of treatment is critical for survival. Untreated, patients survive only a few months. These patients have multisystem involvement and may develop multi-organ failure. The goal of therapy for patients with HLH is to suppress life-threatening inflammation. After induction, patients who are recovering are weaned off therapy, while those who are not improving are continued on therapy as a potential bridge to stem cell transplantation. Monitoring treatment response is critical as treatment escalation may be warranted if the patient is not improving. The distinction between chemotherapy toxicity and worsening disease may be difficult to make clinically. Quite a variety of clinical, biochemical and immunological biomarkers are used at diagnosis and to assess treatment response. The response to initial therapy is a major factor in determining the need for additional therapy including Hematopoietic Cell Transplant (HCT). Response to induction therapy is monitored by assessing the patient clinically and using HLH disease-specific markers. Although this approach has some success, it is sometimes confounded by a new infection or treatment toxicity. Imaging can provide an additional layer of accuracy in the initial evaluation of HLH patients as well as their monitoring and follow-up. 18F-FDG PET scans are highly sensitive and can be quite helpful in the management of these patients (Figure 1).