HHV-6 found to be the most frequent cause of viremia in children following HSCT

A prospective study of children transplanted for both malignant and nonmalignant disease found HHV-6 viremia in 53% of cases.

Yamada et al. from the National Center for Child Health and Development in Tokyo, Japan, prospectively investigated viral loads following HSCT in 74 pediatric patients with malignant and nonmalignant diseases (most often various forms of immunodeficiency). 

Viral DNAemia was found in 52/64 patients (70%). As shown in Figure 1, HHV-6 was the most frequently detected at 53%, followed by CMV (41%). Other viruses detected included BKV (30%), HHV-7 (19%), EBV (18%), adenovirus (5%) and parvovirus B19 (4%). Only one of the 39 patients with HHV-6 viremia experienced a clear associated illness (meningoencephalitis).

Fig 1 – Cumulative rates of viremia in the 100 days following HSCT

Age of greater or equal to 2 years was a significant independent risk factor for HHV-6 DNAemia: Odds ratio (OR) = 10.9 (P=.02). Since primary infection with HHV-6 typically occurs before 2 years of age, this risk factor likely is explained by reactivation of virus as a result of the immunosuppression associated with transplantation. 

CMV viremia was a significant independent predictor of mortality: OR = 5.89 (1.15-30.2, P = 0.03) in a multivariate analysis. HHV-6 viremia also was associated with a substantially increased risk of mortality: OR = 4.81 (0.76 - 30.6, P=0.09). Although the result was not statistically significant, the study was underpowered to recognize the risk as significant, and the odds ratio was high. Multiple studies have found HHV-6 to be associated with increased mortality in transplant patients (Gonzalez 2021Lee 2021, Hill 2019).

Rates of viremia were very similar among the nearly half of the patients who received HSCT for nonmalignant immunodeficiency diseases and the half who suffered from malignant diseases.

This study emphasizes the frequent viremia from reactivation of HHV-6 and other viruses following HSCT in pediatric patients with both malignant and nonmalignant diseases.   Both HHV-6 and HCMV viremia was associated with an increased risk of mortality, although this does not mean that treating the viremia with antivirals would necessarily lower the risk of mortality.  Reassuringly, clinical illness associated with the viremia was infrequent.

Read the full article:  Yamada 2021