Beyond the usual suspects: Unveiling adenovirus–mycoplasma coinfection in severe paediatric pneumonia—A case series

Dear Editor, Community-acquired pneumonia (CAP) remains a major cause of under-five mortality globally, particularly in low- and middle-income countries.[1] While viral pathogens are the predominant cause in young children, Mycoplasma pneumoniae (MP), though rare (~1%), is emerging as a relevant contributor.[2] Traditionally associated with school-aged children, MP is now occasionally identified in younger children. Severe CAP is typically linked to pathogens, like Streptococcus and Staphylococcus, but recent evidence highlights the role of viral–bacterial coinfections in worsening disease severity. Reports from East Asia suggest that adenovirus–MP coinfection is a notable contributor to severe CAP.[3] These coinfections present diagnostic challenges due to overlapping clinical features and limited access to polymerase chain reaction (PCR) in resource-constrained settings. This case series describes three young children with severe CAP and right upper lobe (RUL) collapse due to adenovirus–MP coinfection, unresponsive to standard therapy but resolved with bronchoscopy and targeted treatment. CASE 1 A six-month-old boy presented with four days of fever, cough, coryza, and worsening respiratory distress (RD). Examination revealed a respiratory rate (RR) of 68 breaths/min, retractions, and SpO2 of 86% on room air. Auscultation revealed reduced air entry and bronchial breath sounds over the right mammary region (RMR). Chest X-ray revealed right upper lobe (RUL) collapse/consolidation [Figure 1a] Blood counts were normal (TLC: 9,600/µL, neutrophils 35%) with mildly elevated CRP (9.36 mg/L). Despite empiric antibiotics (amoxicillin/clavulanate) and high-flow nasal cannula (HFNC) support, there was no improvement. The patient’s condition deteriorated despite escalation of antibiotics and chest physiotherapy. Bronchoscopy revealed mucosal damage and mucus plugging in the RUL bronchus (RULB). BAL showed neutrophilia (40%) and PCR confirmed adenovirus and MP. Azithromycin was initiated, leading to recovery. The RUL collapse resolved post-bronchoscopy, and the child was discharged after 13 days.Figure 1: Chest radiographs of three patients (a-c) demonstrating consolidation (asterisk) along with upward displacement of the horizontal interlobar fissure (arrow), indicating right upper lobe collapseCASE 2 A three-year-old girl had a nine-day history of fever, cough, and four days of RD, unresponsive to multiple antibiotics at a peripheral centre. On admission, RR was 52 breaths/min with severe retractions and SpO2 of 84% on 2 L/min oxygen. Respiratory examination showed decreased air entry in the RMR. Chest X-ray revealed RUL collapse [Figure 1b]. TLC was 9,300/µL, and CRP was elevated (56 mg/L). Fever and RD persisted despite treatment. Bronchoscopy revealed RULB plugging with mucosal damage. BAL cytology showed neutrophilia (35%) and PCR confirmed adenovirus–MP. Azithromycin was added, resulting in clinical and radiologic resolution. She was discharged after seven days. CASE 3 A six-year-old boy presented with five days of fever and three days of RD. RR was 34 breaths/min with severe retractions and bronchial breathing over the RMR. Chest X-ray showed RUL collapse/consolidation [Figure 1c]. TLC was 10,600/µL, with lymphocytosis (50%), normal neutrophils (45%), and mildly raised CRP (19.1 mg/L). Bronchoscopy showed mucus plugging and mucosal damage in the RULB. BAL cytology revealed neutrophilia (28%), and PCR confirmed adenovirus and MP. Post-bronchoscopy and azithromycin therapy, the child improved and was discharged after 10 days. All three cases presented with severe CAP, persistent RUL collapse, and poor response to empiric antibiotics, necessitating bronchoscopy. BAL-PCR identified adenovirus–MP coinfection in each case, guiding targeted therapy. MP typically causes gradual respiratory symptoms, progressing to lower respiratory tract infection (LRTI) in rare cases in under-fives.[4] Adenovirus contributes to 5%–10% of paediatric CAP and is capable of causing severe disease, particularly in immunocompromised children.[5] None of our patients had immunocompromising conditions, suggesting disease severity stemmed from the synergistic effect of viral–bacterial coinfection. For instance, Quang KT et al.[6] demonstrated that viral–bacterial coinfection was the most common cause of severe CAP (43.1% cases). Mechanisms, such as reduced bacterial clearance, increased bacterial adherence, and viral suppression of local immunity, promote bacterial growth, while bacterial infections can increase viral production and release from airway epithelial cells.[7,8] Studies by Chen Q. et al.,[3] Li F. et al.,[7] and Gao J. et al.[8] have identified adenovirus–MP coinfection as a marker of severe CAP, often associated with longer fever duration and prolonged hospital stays requiring bronchoscopic interventions. The identification of Mycoplasma pneumoniae as a cause of severe pneumonia in young children in this series challenges its traditional association with older age groups. Similarly, adenoviral pneumonia, often overlooked, was a key contributor to disease severity. The absence of specific lab patterns highlights the need for clinical vigilance in suspecting adenovirus–MP coinfection. Adenovirus–MP coinfection should be considered in children with severe CAP and persistent lung collapse unresponsive to standard therapy. Early diagnosis can guide targeted treatment and help reduce unnecessary antibiotic use. Larger studies are needed to better define its prevalence, especially in resource-limited settings. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.