Background
Mucormycosis in children has emerged as an increasingly important infection and is associated with significant morbidity and mortality [
1,
2]. Mucorales are generally characterized by their tendency for rapid vascular invasion leading to vascular thrombosis and tissue necrosis. As a result, the Mucorales may initially cause localized infections, but they rapidly progress to invasive soft tissue, rhinocerebral, orbital, gastrointestinal or pulmonary infections [
2,
3].
Risk factors for mucormycosis in adults include profound and prolonged neutropenia, hematological malignancies, bone marrow or solid organ transplantation, uncontrolled diabetes mellitus with metabolic acidosis, iron overload, deferoxamine therapy, previous trauma, whereas in few cases no apparent underlying condition can be identified [
4‐
10]. In paediatric reviews, prematurity has also been a risk factor for invasive mucormycosis, and age <12 months was an independent risk factor for mortality [
1,
11,
12]. While some investigators have shown an increasing incidence in adults [
13], the epidemiological data in children are too limited as to provide epidemiological trends [
2]. Due to the rarity of the disease and the limited awareness of physicians to diagnose and record these cases, the true burden in the paediatric setting is difficult to be estimated.
The aim of this study was to collect and analyse data of paediatric mucormycosis cases from two international case registry databases to update and broaden our knowledge on epidemiology, clinical characteristics, diagnostic procedures, microbiology, treatment and outcome of mucormycosis in children.
Methods
Study design
The study was a combined analysis of prospectively collected cases enrolled in two international invasive fungal disease (IFD) registries: Zygomyco.net and FungiScope™. Both databases were searched for invasive infections due to Mucorales in paediatric (≤19 years) patients. Cases diagnosed between 2005 and 2014 were extracted from the registries and analysed. The selection of the study period was based on the availability of data in the two registries.
Zygomyco.net was created in 2004 as a European registry and later became a global registry for invasive mucormycosis of the European Confederation of Medical Mycology/International Society for Human and Animal Mycology (ECMM/ISHAM) Working Group on Zygomycosis. For this database, a national coordinator in each participating European country was appointed to prospectively collect and record confirmed cases in standardized case report forms (CRFs) at
www.zygomyco.net, which were then sent either by e-mail or fax to the general study coordinator (GP). The national coordinators were internationally recognized experts in the field of fungal infections, and in most cases they were appointed by the respective national mycology societies. Diagnosis of cases was based on standard mycological tools and when isolate was available by molecular methods in two central laboratories [
9].
FungiScope™ – Global Emerging Fungal Infection Registry (ClinicalTrials.gov NCT01731353) was created in 2003 as an international university-based case registry that collects data of patients with rare IFD, using a web-based electronic case form at
www.fungiscope.net. The survey was hosted by ClinicalSurveys.net, an internet-based survey software.
For both databases case registration was on a voluntary, non-systematic basis. Data sets were submitted in a pseudonymized form and regularly checked for completeness with queries made in written form for missing data. Follow-up information was repeatedly requested regarding treatment response, survival or death. If follow-up could not be continued at all requests, outcome at last contact was used.
The final analysis of the dataset was performed after checking for and deleting overlapping cases enrolled in both registries. The final combined database included the following variables: gender, age, diagnostic procedures for documenting infection, anatomic location, underlying conditions, microbiology, management and outcome.
Definitions
The term mucormycosis was used in this study as a synonym of zygomycosis [
14]. Mucorales are one of the two orders comprising Zygomycetes, that is Mucorales and Entomophthorales [
14]. In particular, Mucorales consist of genera including
Rhizopus, Mucor, Lichtheimia (Absidia), Cunninghamella and
Saksenaea.
For the present study, a paediatric patient was defined as an individual ≤19 years of age.
The day of diagnosis was defined as the day on which the first diagnostic procedure identifying a Mucorales was performed. For patients with a diagnosis obtained during post-mortem examination, the day of death was considered to be the day of diagnosis.
Classification of infection
The sites of infection were classified according to those utilized in the study of Roden et al
. [
15]
. Accordingly, dissemination was defined as two or more non-contiguous locations of Mucorales infection; sino-orbital disease as involvement of the paranasal sinus and orbit, without extension to the brain; pulmonary infection as localised when confined to lung tissue and as deep extension when invading adjacent tissues. Cutaneous infection was characterized as localised when it did not extend to underlying tissues, in which case it was characterized as having localized soft tissue infection.
For the classification of each case as proven or probable, the revised definitions of IFD of the European Organization for Research and Treatment of Cancer/Mycosis Study Group (EORTC/MSG) were used [
16]. Proven mucormycosis was defined when both histology and culture [or polymerase chain reaction (PCR)] existed and probable mucormycosis when only histology (proven IFD) or positive culture from a normally non-sterile site.
Outcome was defined as survival or mortality at last contact of follow-up. Mortality was assessed as all-cause mortality during the course of mucormycosis.
Statistical analysis
Statistical analysis was conducted using SPSS v.12. Differences between the qualitative variables in two or more groups were analysed by chi-square test. A two-sided p value of <0.05 was considered significant. For the estimation of predictors of outcome univariate analysis was performed using logistic regression for each variable separately. The variables for which a statistically significant relationship was shown (p <0.05) were used to construct a new multivariate model using the logistic regression approach. In the final regression analysis lost-to-follow up cases were excluded.
Ethics
Recording patients’ data in the zygomyco.net and analysing them was approved by the Ethics Committee of the National and Kapodistrian University Attikon General Hospital located in Athens, Greece, the institution of the registry principal investigator (reference 9/30-8-2011). Informed consent was obtained if required by local laws or regulations. Ethics Committees that approved data collection and use for this registry are in Additional file
1.
Similarly, to record patients’ data in FungiScope™ informed consent was obtained if required by local laws or regulations. The ethics committee at University of Cologne, Germany, confirmed the data protection and privacy policy (reference-ID 05-102) [
17]. Ethics Committees that approved the protocol for data collection and use in the Fungiscope registry are in Additional file
2.
Discussion
This is the largest multinational analysis of contemporary data of paediatric mucormycosis cases based on electronic recording in two independent global registries. Based on the results of the present study, mucormycosis in children seems to be a rather heterogeneous infectious disease as far as mortality rate is concerned. This is directly associated with the dissemination of the infection and the underlying condition of the patients. In particular, although the crude mortality rate for the whole paediatric cohort was 33.3 %, the percentage of children who died with disseminated mucormycosis was significantly higher (61 %) compared to the children with localized disease (0 %). Furthermore, in children suffering from malignancies the mortality rate ranged from 41.3 % to 66.6 %, while in children without any underlying condition the mortality rate was relatively low (16.6 %). The multivariate analysis confirmed the observations of the initial descriptive analysis revealing that two of the main independent significant factors influencing mortality in paediatric mucormycosis were disseminated infection and HSCT. These results emphasize the need for high awareness and prompt diagnosis especially during severe immunocompromise. Mucorales rapidly invade vessels and disseminate, thus antifungal therapy combined with surgical debridement significantly impacted on mortality in our multivariate analysis. Irrespective from other confounding variables, children receiving antifungal therapy and surgery had a mortality rate of 18.5 %, while patients receiving antifungal therapy alone or no therapy at all reached a mortality rate of 60 % and 100 %, respectively. The abovementioned results should be interpreted with caution since the rather small sample size of the children precluded weighing for potential confounding factors.
Haematological malignancies and HSCT predominated as underlying conditions. DM was present in only 5 %, while in 10 % of the children no predisposing factor was identified. The predominance of immunocompromised patients could be explained either by increase of the frequency of such children worldwide or by reporting bias and increased awareness of haematology centers to participate and include cases in registries. In the largest subgroup of immunocompromised children, as depicted in Table
2, disseminated and pulmonary infection were found, in concordance with previous literature, as the most frequent sites of infection. By comparison, localized skin and soft tissue infections or sinus infections were more frequently detected in cases associated with trauma/surgery or without any underlying condition [
1,
2,
9,
10,
19]. DM was not associated with rhinocerebral mucormycosis possibly due to the small number of DM cases [
9,
15,
19]. In a previous review article, gastrointestinal (GI) infections accounted for almost 20 % of children with mucormycosis, but the majority of these patients were neonates, in which the final diagnosis was placed post-mortem [
1]. This might have led to underrepresentation of this patients’ group in the registries of the present study. However, we observed few GI infections recorded as part of disseminated disease, possibly due to delay in diagnosis of mucormycosis. Additionally, the median age in the review [
1] was 5 years with a respectable number of infants, while the median age in our registry study was 13 years with a small proportion of cases below one year of age (8 %). Irrespectively of the exact percentages of underlying conditions it is important to emphasize that infections due to Mucorales are observed in rather heterogenic paediatric populations with a wide spectrum of organ involvement and subsequently with significant differences in treatment approach and outcome.
The distribution of Mucorales revealed that
Rhizopus spp. remains the most frequent species isolated in children, followed by
Lichtheimia spp. Of interest, in a previous systematic review of published paediatric cases, the second most frequent specie isolated was
Mucor sp. [
1]. According to a recent epidemiological study by
Lanternier et al. the prevalence of
Lichtheimia spp. in Europe ranges from 18 % to 24 %, while in similar studies from Asia and the US
Lichtheimia spp. are recorded with a frequency of <10 % [
19]. In our study, the majority of data derived from European countries (54 cases) and the percentage of
Lichtheimia spp. recorded was almost 16%. Based on this information, the percentage of
Lichtheimia spp. in our study may not directly reflect an actual epidemiological rise of these species in children. However, it may represent different fungal biogeography distribution among European and non-European countries that needs further confirmation with extended analysis of the local fungal niches worldwide.
Treatment options against mucormycosis consisted mainly of combined therapy (antifungal therapy and surgery) recorded in 47.6 % or of antifungal therapy alone reported in almost 40 % [
9,
20]. Amphotericin B was the drug of choice given either as monotherapy (31.7 %) or in combination with other antifungal agents. The superiority of AmB monotherapy or combination therapy compared to other therapeutic options against Mucorales infections was observed in a previously published study with solid organ transplantation (SOT) patients suffering from mucormycosis. This study concluded that AmB might influence overall survival. However, in other studies the choice of first line antifungal therapy did not significantly influence the survival rates of the patients [
9,
10,
19]. In our study, the impact of AmB as monotherapy or combined with other antifungals on overall survival could not be estimated, because the number of patients taking the various antifungals with AmB was too small and a statistical comparison was not feasible. In addition, concomitant confounding factors hindered further analysis of the present data. On the other hand, in our study combined antifungal therapy plus surgery remained an independent factor for survival. Results from previous studies are rather controversial. One study showed that surgery in adult patients does not significantly influence overall survival, while other studies stressed that surgery alone improves outcome, especially in SOT patients [
1,
9,
15,
19,
21]. We can hypothesize that in localized infections surgery improves outcome by hindering dissemination, while in severely sick patients, combination of antifungal drugs plus surgery significantly reduces the overall burden of disease.
In the present study, further independent risk factors for mortality were dissemination and HSCT. These results are in concordance with previous data [
19]. Thus, age <12 months was also an independent risk factor for mortality in paediatric patients, which was not the case in our case series, although these differences may also be partially explained by the significant differences in the median age of the children [
1,
9,
19]. The overall mortality rate was 33.3 %. As expected, the mortality rates presented great variability among different anatomic sites and underlying conditions. In particular, localized infection and no underlying conditions or trauma presented the highest survival rates, while disseminated infection and HSCT were associated with increased mortality rate.
Limiting factors of the present study were associated with the nature of its design that was based on the extraction and evaluation of data from two differently organized global registries. This has led to the collection and careful analysis only of variables/data with exactly the same characteristics, such as definitions, stratifications, data recorded. For that reason clinical presentation of the cases as well as epidemiological time trends of paediatric mucormycosis were not analysed in the present study. A correlation between the specific countries and the variables presented in the study could be very useful to detect possible differences among cases worldwide. It is probable that the number of mucormycosis cases in each country in the present study does not necessarily reflect the country-specific rates of the disease, but the awareness of the investigators to report the cases in the two databases. Additionally, several countries reported only one to two cases during the study period therefore a statistical analysis between the variables and the specific counties was not feasible. In an attempt to detect differences in pediatric mucormycosis cases between EU and non-EU countries our analysis showed that there was no statistical difference reported as far as age, causative pathogens and survival is concerned. This result should be interpreted with caution since the number of non-EU cases was small to draw conclusions. On the other hand, due to the rarity of the disease, previous data from the literature until now were mainly extracted from i) mixed adult-children population databases with a limited number of paediatric cases, ii) very small paediatric case series or iii) literature review analyses [
1,
2,
9,
10,
12]. In that sense, this is a first time of prospectively collecting and analysing global contemporary cases of mucormycosis in children.
One of the major strengths of the present study is the “merging” of data in order to obtain a satisfactory pediatric sample. This is prerequisite in order to obtain results with sufficient statistical power and to draw conclusions for rare fungal diseases. Beyond the limitations mentioned, the present study increases the degree of awareness of this potentially fatal disease among physicians and offers further important information enriching our knowledge on epidemiology and current management of invasive mucormycosis in the paediatric setting from two international databases.
Acknowledgement
Financial support has been given by European Confederation of Medical Mycology (ECMM).
Results of this study were presented at the Joint 55th Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) and 28th International Congress of Chemotherapy (ICC) Meeting, San Diego CA, September 2015.
*Collaborators of Zygomyco.net and/or FungiScope™:
Anupma Kindo (Sri Ramachandra Medical College and Research Institute, Porur, Chennai, Tamil Nadu, India); Alberto Arencibia Núñez (Hematology and Immunology Institute, Havana, Cuba; currently affiliated with Hernan Henrique Aravena Hospital, La Frontera University, Temuco, Chile); Fabianne Carlesse (Federal University of São Paulo, São Paulo, Brazil); Jagdish Chander (Government Medical College Hospital, Chandigarh, India); Cornelia Lass-Flörl (Innsbruck Medical University, Innsbruck, Austria); Bertrand Dupont (Necker hospital, Paris, France); Werner Heinz (University of Würzburg Medical Center, Würzburg, Germany); Nikolay Klimko and Sofya Khostelidi (Metchnikov North-Western State Medical University, St Petersburg, Russia); Katrien Lagrou (KU Leuven-University of Leuven, Leuven, Belgium); Livio Pagano (Catholic University of Sacred Heart, Rome, Italy); Zdenek Racil and Monika Rolencova (University Hospital Brno, Brno, Czech Republic); Petr Sedlacek and Vanda Chrenkova (University Hospital Motol, Praha, Czech Republic); Julia Horakova (Children’s University Hospital Bratislava, Slovakia); Peter Mudry (Masaryk University and University Hospital Brno, Czech Republic); Maria JGT Vehreschild (University Hospital of Cologne, Cologne, Germany); Stefan Zimmerli (Bern University Hospital, Bern, Switzerland).
Competing interests
ZDP has no financial and non-financial competing interests.
DS has no financial and non-financial competing interests.
ER reports grants, and non-financial support from Astellas, Pfizer, Gilead, and Merck, outside the submitted work.
AHG reports grants, personal fees, and non-financial support from Amplyx, Astellas, Basilea, Gilead, Merck, Sharp & Dohme, Schering-Plough, Pfizer, and Zeneus/Cephalon.
AS reports financial support from Gilead, Astellas, Pfizer and Merck, outside the submitted work.
GP reports financial support from Gilead, Astellas, Pfizer and Merck outside the submitted work.
OC reports research grants from, is an advisor to, or received lecture honoraria from 3M, Actelion, Amplyx, Anacor, Astellas, AstraZeneca, Basilea, Bayer, Celgene, Cidara, Cubist/Optimer, Da Volterra, Duke University (NIH UM1AI104681), F2G, Genentech/Roche, Gilead, GSK, Inositec AG, Janssen Pharmaceuticals, Leeds University, Matinas, Medpace, MSD, Miltenyi, NanoMR, Paratek Pharmaceuticals, Pfizer, Quintiles, Sanofi Pasteur, Scynexis, Seres, Summit, The Medicine Company, Vical, Vifor.