Analysis of five cases of human herpesvirus-6 myelitis among 121 cord blood transplantations

Association between human herpesvirus-6 encephalitis and antiviral prophylaxis after allogeneic hematopoietic stem cell transplantation in the letermovir era

The impact of letermovir (LTV)-an anti-cytomegalovirus (CMV) drug-on human herpesvirus-6 (HHV-6) encephalitis is unclear. We hypothesized that LTV prophylaxis may increase the incidence of HHV-6 encephalitis by reducing anti-CMV therapies after allogeneic hematopoietic stem cell transplantation (HSCT). To evaluate the association between HHV-6 encephalitis and antiviral prophylaxis, 7985 adult patients from a nationwide registry who underwent their first HSCT between January 2019 and December 2021 were analyzed. The incidence of HHV-6 encephalitis on day 100 after HSCT was 3.6%; 11.5% for the broad-spectrum antiviral group (foscarnet, ganciclovir, or valganciclovir); 2.8% for the LTV group, and 3.8% for the other antiviral group (p < 0.001). These differences persisted when cord blood transplantation (CBT) was analyzed separately (14.1%, 5.9%, and 7.4%, p < 0.001). In the multivariate analysis, CBT (hazard ratio [HR]: 2.90), broad-spectrum antiviral prophylaxis (HR: 1.91), and grade II-IV acute graft-versus-host disease requiring systemic corticosteroids (HR: 2.42) were independent risk factors for encephalitis (all p < 0.001). The findings of this large modern database study indicate that broad-spectrum antiviral prophylaxis, rather than LTV prophylaxis, is paradoxically associated with HHV-6 encephalitis in the LTV era. This paradoxical finding needs to be further explored in future studies.

Nelarabine-induced myelopathy in patients undergoing allogeneic hematopoietic cell transplantation: a report of three cases

Nelarabine is an effective treatment for T-cell acute lymphoblastic leukemia/lymphoma. Myelopathy is a rare but serious adverse event associated with this drug. Three patients who received nelarabine at the National Cancer Center Hospital from December 2014 to March 2021 developed myelopathy 20 days before, 12 days after, and 29 days after allogeneic hematopoietic cell transplantation (allo-HCT), respectively. Magnetic resonance imaging showed that two of the patients had lesions in the dorsal column or medulla oblongata, and one had no abnormalities in the head or spine. Despite treatment with intravenous immunoglobulin and methylprednisolone, all patients became unable to walk. One patient died on day 101 after allo-HCT due to progressive neurotoxicity. The other two patients showed spontaneous improvement in neurological symptoms, but one died of mucormycosis on day 476. Autopsy revealed spongiosis in the posterior funiculus in both patients who died, and also in the medulla oblongata in one patient. In the surviving patient, positron emission tomography on day 84 showed abnormal accumulation, suggesting continued inflammation. These cases demonstrated pathophysiological features of nelarabine-induced myelopathy and indicate that allo-HCT may worsen the condition. It is necessary to elucidate the underlying mechanism and establish diagnostic methods and therapies.

Acute infectious myelopathies

PURPOSE OF REVIEW

The patient who presents with an acute spinal cord syndrome with weakness/paralysis of the limbs presents a diagnostic. Two important syndromes are acute transverse myelitis (ATM) and acute flaccid paralysis (AFP). Both can be caused by a number of infectious and noninfectious causes. Since 2014 there have been outbreaks of acute flaccid myelitis (a subgroup of AFP) in the United States, with a national surveillance program underway. In addition, there have been increasing reports of ATM from new and emerging pathogens, and opportunistic infections in immunocompromised hosts.

RECENT FINDINGS

Infectious causes of ATM or AFP need to be ruled out first. There may be important clues to an infectious cause from epidemiologic risk factors, immune status, international travel, MRI, and laboratory findings. We summarize key features for the more common pathogens in this review. Advances in laboratory testing have improved the diagnostic yield from cerebrospinal fluid, including real-time polymerase chain reaction, metagenomic next-generation sequencing, and advanced antibody detection techniques. These tests still have limitations and require clinical correlation.

SUMMARY

We present a syndromic approach to infectious myelopathies, focusing on clinical patterns that help narrow the diagnostic possibilities.

HHV-6: an unusual cause of cerebellar ataxia

Human herpesvirus 6 (HHV-6) infection is the cause of roseola infantum in children. The reactivation of HHV-6 is associated with multiple clinical syndromes including encephalitis and myelitis, especially in haematopoietic stem cell transplant recipients. However, the virus can cause encephalitis in other immunosuppressed as well as immunocompetent individuals. We report a case of a 70-year-old woman who was immunocompromised secondary to treatment of rheumatoid arthritis with leflunomide and methotrexate. The patient presented with acute ataxia, diplopia and dysarthria. MRI brain showed an enhancing lesion in the midbrain. The diagnosis of HHV-6 encephalitis was made after HHV-6 A DNA was detected in both serum and cerebrospinal fluid. Treatment consisted of a 3-week course of intravenous ganciclovir along with physiotherapy. At a 3-month follow-up, repeat MRI brain showed a decrease in size and oedema of the lesion and the patient's neurological function was improved.

Clinical characteristics of human herpesvirus-6 myelitis after allogeneic hematopoietic stem cell transplantation and its favorable outcome by early intervention

After allogeneic hematopoietic stem cell transplantation (HSCT), human herpesvirus-6 (HHV-6) can cause serious central nervous system (CNS) disorder and typically presents as encephalitis. Another manifestation of HHV-6 is myelitis, which has not been fully evaluated. In this study, we retrospectively analyzed 19 patients who developed HHV-6 myelitis after allogeneic HSCT. Median onset was 20 days after transplantation (range, 13-31), with a cumulative incidence of 4.1% at day 40 after transplantation. Median age at transplant was 50 years (range, 17-61). Median copy number of HHV-6 DNA was 3000 copies/ml in cerebrospinal fluid (CSF; range, 200-100,000). The most common symptoms were pruritus, pain of the extremities/back, and numbness. Three patients subsequently developed encephalitis in the clinical course of myelitis; their HHV-6 copy numbers in CSF had been higher than 10,000 copies/ml at the onset of myelitis. Antiviral agents were initiated shortly after onset in all patients, resulting in recovery. These results suggest that myelitis would be an important subtype of HHV-6-associated CNS disorders after allogeneic HSCT, whose prognosis could be favorable by an early intervention. Transplant physicians should recognize early posttransplant neurological symptoms such as pruritus, pain, or numbness as possible signs of HHV-6 myelitis, which could also progress to encephalitis.

Guidelines from the 2017 European Conference on Infections in Leukaemia for management of HHV-6 infection in patients with hematologic malignancies and after hematopoietic stem cell transplantation

Of the two human herpesvirus 6 (HHV-6) species, human herpesvirus 6B (HHV-6B) encephalitis is an important cause of morbidity and mortality after allogeneic hematopoietic stem cell transplant. Guidelines for the management of HHV-6 infections in patients with hematologic malignancies or post-transplant were prepared a decade ago but there have been no other guidelines since then despite significant advances in the understanding of HHV-6 encephalitis, its therapy, and other aspects of HHV-6 disease in this patient population. Revised guidelines prepared at the 2017 European Conference on Infections in Leukaemia covering diagnosis, preventative strategies and management of HHV-6 disease are now presented.