DRESS/DIHS is one of the most serious delayed-type adverse drug reactions encountered in clinical medicine. It is characterized by a widespread skin eruption, fever, systemic inflammation, involvement of internal organs such as the liver, hematologic abnormalities including atypical lymphocytes, and, in many cases, reactivation of human herpesvirus 6, or HHV-6. The syndrome typically develops two to six weeks after exposure to the culprit drug, a latency that distinguishes it from immediate hypersensitivity reactions. Mortality is significant, particularly when liver involvement is severe, and recognition depends on scoring systems such as RegiSCAR that integrate rash morphology, fever, lymphadenopathy, blood count abnormalities, organ involvement, and viral reactivation. In immunocompetent patients, the diagnostic constellation is usually recognizable, but the syndrome’s presentation can be substantially altered in patients whose immune systems have been profoundly suppressed by chemotherapy.

CPX-351, marketed as Vyxeos, is a dual-drug liposomal encapsulation designed to optimize the synergistic molar ratio of cytarabine to daunorubicin and to prolong their exposure within the plasma. It is approved for treatment-related acute myeloid leukemia and acute myeloid leukemia with myelodysplasia-related changes, populations in which intensified traditional induction regimens carry prohibitive toxicity. Skin eruptions are common adverse events with CPX-351, and one of the most frequent cutaneous findings in these patients is toxic erythema of chemotherapy, or TEC, a benign and self-limited eruption that typically affects the hands, intertriginous areas, and trunk within days of drug exposure. Distinguishing TEC from an evolving DRESS/DIHS-like reaction is difficult, and the new case illustrates precisely how the two conditions can overlap in their earliest phases.

In the reported patient, the cutaneous story began with an early eruption localized to the intertriginous areas and trunk, a distribution and timing initially compatible with toxic erythema of chemotherapy. Had the eruption followed the usual course, it would have been expected to stabilize and resolve without intervention. Instead, the clinical picture deteriorated. The patient developed recurrent fevers, and the eruption progressed to generalized erythema covering more than 90 percent of his body surface area. Accompanying features included lymphadenopathy, the appearance of atypical lymphocytes in the peripheral blood, and elevation of liver enzymes, each of which is a recognized component of the DRESS/DIHS diagnostic framework. Taken together, these findings shifted the clinical suspicion away from benign toxic erythema and toward a systemic drug hypersensitivity syndrome.

Several laboratory investigations provided pivotal diagnostic clues. Most strikingly, quantitative polymerase chain reaction demonstrated a markedly elevated HHV-6 DNA level of 1.2 million copies per milliliter of blood. HHV-6 reactivation is considered a signature feature of classic DRESS/DIHS, occurring in the majority of typical cases, and its detection in this severely lymphopenic patient served as a strong corroborating marker of the syndrome. At the same time, the case defied several conventional expectations. The patient had severe chemotherapy-induced lymphopenia, there was no peripheral eosinophilia, skin histology revealed inconspicuous dermal eosinophils, and serum thymus and activation-regulated chemokine, known as TARC and often used as a biomarker of DRESS/DIHS, was at a normal level. The authors emphasize that these deviations are precisely what made the diagnosis so difficult, since eosinophilia and elevated TARC are among the criteria clinicians most commonly rely upon.

A skin biopsy provided additional support for the diagnosis. Histopathologic examination showed interface dermatitis with superficial perivascular lymphocytic infiltration, a pattern consistent with a delayed hypersensitivity reaction rather than the necrotic keratinocytes and eccrine involvement more characteristic of toxic erythema of chemotherapy. Interface dermatitis, in which lymphocytes attack the basal layer of the epidermis, is a histologic hallmark seen in many drug-induced eruptions, including DRESS/DIHS, and its identification helped consolidate the clinical and laboratory findings into a coherent diagnosis despite the absence of eosinophils in the dermal infiltrate.

Treatment with systemic prednisolone produced a rapid and convincing response. The patient’s fever resolved promptly, appetite improved, the extensive skin lesions began to heal, atypical lymphocytes disappeared from the circulation, and HHV-6 DNA became undetectable. The temporal relationship between corticosteroid initiation and the simultaneous resolution of inflammatory, cutaneous, and virologic abnormalities is characteristic of DRESS/DIHS and further reinforced the diagnostic conclusion. Importantly, the patient was subsequently able to proceed to conditioning therapy and umbilical cord blood transplantation, meaning that recognition and treatment of the hypersensitivity reaction did not derail his definitive leukemia management.

Attribution of the reaction to CPX-351 required careful weighing of alternatives, and the authors frame the association as possible rather than definitive. The temporal relationship between CPX-351 administration and the onset of the reaction was the principal basis for implicating the drug, but the authors explicitly note that toxic erythema of chemotherapy and concomitant medications represented important alternative considerations. Patients with acute myeloid leukemia typically receive multiple supportive agents, including antimicrobials, antifungals, and antivirals, several of which are themselves recognized causes of DRESS/DIHS. In addition, the leukemia itself and its complications can produce fever, rash, hepatic dysfunction, and lymphadenopathy. The heterogeneity of the clinical environment in hematology patients means that drug causality assessment in this population is intrinsically uncertain, and the report’s cautious language reflects this reality.

Beyond its immediate clinical message, the case carries broader implications for how DRESS/DIHS is understood and diagnosed. Classical descriptions assume a relatively intact immune system capable of mounting the full hypersensitivity phenotype, including expansion of drug-specific T cells, eosinophil recruitment through interleukin-5, and elevated TARC production by activated lymphocytes. A patient with profound chemotherapy-induced lymphopenia lacks the cellular substrate for many of these features, and the reported case demonstrates that the syndrome can nonetheless develop in this setting. This suggests that current diagnostic criteria, which award points for eosinophilia, atypical lymphocytes, and lymphadenopathy, may underdiagnose DRESS/DIHS in severely immunocompromised patients. The authors propose that HHV-6 reactivation may serve as a particularly valuable diagnostic marker when eosinophilia is absent, since viral reactivation appears to depend on mechanisms that can persist despite lymphocyte depletion.

The report also offers practical guidance for clinicians who treat high-risk acute myeloid leukemia with CPX-351. Skin eruptions during therapy should not automatically be dismissed as toxic erythema of chemotherapy, particularly when they progress beyond the typical distribution, persist or worsen after the expected time course, or are accompanied by recurrent fever, lymphadenopathy, hepatic enzyme elevation, or atypical lymphocytes. In such circumstances, measurement of HHV-6 DNA and consideration of a DRESS/DIHS-like reaction are warranted even in the face of severe lymphopenia and absent eosinophilia. Early recognition matters because untreated DRESS/DIHS can progress to fulminant hepatic failure and death, while timely systemic corticosteroids, as demonstrated in this patient, can produce rapid clinical improvement and allow the underlying leukemia treatment plan, including allogeneic transplantation, to continue on schedule. As CPX-351 use expands worldwide, the authors suggest that clinicians maintain heightened awareness that this liposomal chemotherapy regimen, like many other drugs, may in rare cases trigger systemic hypersensitivity, and that its cutaneous and systemic fingerprints may look different in the immunosuppressed host than in the patients in which the syndrome was first described.

Subject of Research: Possible CPX-351-associated DRESS/DIHS-like drug hypersensitivity reaction during severe lymphopenia in acute erythroid leukemia

Article Title: Possible CPX-351-associated drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome-like reaction during severe lymphopenia

Article References: Bamba, S., Kanda, J., Hada, M., Kubota, Y., Nakajima, S., Nomura, T., Fukutome, T., Tsuji, K., & Takaori-Kondo, A. (2026). Possible CPX-351-associated drug reaction with eosinophilia and systemic symptoms/drug-induced hypersensitivity syndrome-like reaction during severe lymphopenia. Annals of Hematology. https://doi.org/10.1007/s00277-026-07282-9

Image Credits: AI Generated

DOI: 10.1007/s00277-026-07282-9

Keywords: CPX-351, DRESS, DIHS, HHV-6, acute myeloid leukemia, drug hypersensitivity, lymphopenia, skin eruptions, TARC, interface dermatitis, toxic erythema of chemotherapy, Annals of Hematology

CPX-351 is not an ordinary chemotherapy combination. It encapsulates cytarabine and daunorubicin within liposomes at a fixed five-to-one molar ratio, allowing the two agents to be delivered together and to persist in the bloodstream for longer than conventional formulations. This pharmacokinetic profile improves drug uptake by leukaemic blasts and has demonstrated clinical benefit for patients whose disease arises from prior therapy or carries myelodysplasia-related genetic changes, groups that historically fared poorly with standard induction regimens. Because the drug can be administered in both inpatient and outpatient settings, clinicians have increasingly explored ambulatory delivery as a way to spare hospital beds, reduce exposure to nosocomial infections, and preserve patients’ autonomy during a demanding course of intensive treatment.

To formalize this practice, a steering group of nine haematologists with hands-on experience in outpatient CPX-351 treatment was assembled from institutions across Europe and Australia. The group drafted a series of consensus statements organized into six key domains covering patient selection, definitions of treatment settings, the anticipated benefits of outpatient care, patient and caregiver requirements, healthcare system prerequisites, and practical measures for optimizing delivery. Their statements were then subjected to validation by a much wider panel: an online survey of 200 haematologists drawn from Australia, France, Germany, Italy, the United Kingdom, and Spain, all of whom had experience with intensive chemotherapy and outpatient care for AML. Agreement was measured on a four-point Likert scale, with consensus defined as at least seventy-five percent agreement for each statement.

The results were strikingly decisive. Forty-two of the forty-three statements, ninety-eight percent of the total, achieved consensus, and thirty-one of them reached agreement levels of ninety percent or higher. Such near-unanimity among two hundred specialists spanning six countries and diverse healthcare systems is uncommon in Delphi studies and signals that the clinical community has converged on a coherent view of how outpatient CPX-351 delivery should be approached. High alignment emerged particularly around the identification of suitable patients and the definition of what constitutes an appropriate outpatient treatment setting, the foundational questions that determine whether a given individual can safely receive intensive liposomal chemotherapy without overnight admission to a hematology ward.

When it came to the benefits of outpatient treatment, the panel expressed its strongest agreement on potential advantages for hospital resourcing, an issue of acute relevance as many hematology units face chronic bed shortages. Respondents also strongly endorsed improvements in patients’ physical and psychological status and in quality of life, reflecting a broader movement in oncology toward care models that respect patients’ daily lives. For older or comorbid patients with t-AML or AML-MRC, who may already be coping with the consequences of prior malignancy treatment, the ability to undergo induction chemotherapy while sleeping in their own beds, staying connected to family, and avoiding the disorientation of prolonged hospitalization carries real therapeutic and emotional weight.

The consensus did not shy away from the prerequisites that make such a model viable. The survey highlighted significant agreement on key patient and caregiver requirements, including cognitive and physical abilities sufficient to recognize and report emerging problems, reliable communication channels with the treating team, and reasonable access to the hospital or an affiliated emergency facility. These criteria acknowledge the central paradox of ambulatory intensive chemotherapy: the treatment is administered outside the ward, but the risk of febrile neutropenia, bleeding, and other complications remains, so patients must be selected, educated, and supported with the same rigor applied to any inpatient induction regimen.

Healthcare system requirements formed another domain of strong agreement. Respondents emphasized the need for explicit hospital protocols, adequate available resources, and robust systems for managing complications when they arise. In practice, this means that outpatient CPX-351 programs cannot simply be layered onto existing services without investment. They demand dedicated staff training, clearly defined escalation pathways, rapid-access clinics or equivalent mechanisms for same-day assessment, and coordination across the multidisciplinary team, including haematologists, nurses, pharmacists, and emergency physicians who may encounter these patients between scheduled visits. The consensus framework effectively functions as a checklist for institutions considering launching such a service.

Beyond eligibility and infrastructure, the panel endorsed a set of practical measures to optimize day-to-day delivery. These included the use of patient assessment tools to standardize selection and monitoring, structured collection of patient feedback, ongoing staff education, deliberate coordination among multidisciplinary team members, and the systematic sharing of best practices across centers. Although the authors acknowledge that challenges may differ across countries and healthcare settings, with reimbursement structures, geographic distances, and staffing models varying widely, the consensus provides clear, transferable guidance on safe and effective outpatient administration. For centers with less experience in ambulatory delivery of CPX-351, the document offers a ready-made starting point grounded in the collective judgment of the international hematology community.

The significance of this work extends beyond a single drug. Intensive chemotherapy for acute myeloid leukaemia has traditionally been synonymous with weeks of hospitalization, a model that burdens patients, families, and health systems alike. As liposomal and targeted therapies broaden the options for older and frailer patients, and as ambulatory care models prove their worth in other malignancies, structured consensus documents like this one will play an increasingly important role in translating clinical trial evidence into safe everyday practice. The near-total agreement achieved here suggests that outpatient CPX-351 treatment for t-AML and AML-MRC is no longer an experimental convenience but an emerging standard of care, provided that centers adhere to the patient-selection criteria, monitoring requirements, and multidisciplinary safeguards that the international panel has now so clearly defined.

Subject of Research: Outpatient delivery of CPX-351 liposomal cytarabine-daunorubicin for therapy-related acute myeloid leukaemia and AML with myelodysplasia-related changes

Article Title: Optimising CPX-351 (liposomal cytarabine-daunorubicin) treatment for t-AML/AML-MRC patients in the outpatient setting: a modified Delphi consensus

Article References: Mehta, P., Martínez-Roca, A., Cahalin, P., McNamara, C., Salamero, O., Martelli, M. P., Franke, G.-N., Capelli, D., de Andrés-Nogales, F., Francia, R., Lassman, E., & Conn, J. (2026). Optimising CPX-351 (liposomal cytarabine-daunorubicin) treatment for t-AML/AML-MRC patients in the outpatient setting: a modified Delphi consensus. Annals of Hematology. https://doi.org/10.1007/s00277-026-07220-9

Image Credits: AI Generated

DOI: 10.1007/s00277-026-07220-9

Keywords: CPX-351, acute myeloid leukaemia, t-AML, AML-MRC, liposomal cytarabine-daunorubicin, outpatient care, Delphi consensus, haematology, chemotherapy, ambulatory care, patient selection, quality of life