Rhinovirus and Mycoplasma pneumoniae Co-infection in Pediatric Patients: Atypical Presentations With Renal Complications

To the Editors: Mycoplasma pneumoniae is known to cause a wide range of extrapulmonary diseases affecting multiple organs in the human body, while human rhinovirus infection similarly has the potential to cause serious complications in both the lungs and other body systems.1 We present 2 pediatric cases of M. pneumoniae and rhinovirus coinfection that led to renal complications, highlighting the importance of recognizing atypical presentations in viral respiratory infections. CASE 1 A 13-year-old male presented with a 15-day history of runny nose, cough, sputum and fever. After initial symptomatic treatment, he developed macroscopic hematuria and was admitted again 5 days later. His history included Henoch-Schönlein purpura in 2019. Physical examination and growth indices were normal, with no edema or abnormal vital signs. Laboratory analyses showed leukocytes of 20.66 x 103/μL, neutrophils 15.3 x 103/μL, lymphocytes 4.34 x 103/μL, platelet count of 496000/mm3, hemoglobin 10.3 g/dL, C-reactive protein 90 mg/L, serum albumin 39 g/dL, antistreptolysin O 1411 IU/mL, complement factors C3 1.92 mg/dL (normal range), C4 0.30 mg/dL (normal range). Renal function tests revealed elevated values compared with baseline, including creatinine (0.98 mg/dL) and urea (40 mg/dL). Liver enzymes and serum immunoglobulin levels were in the normal range for age. Urine analysis showed 141 red blood cells per high-power field, with a microalbumin-to-creatinine ratio of 353 mg/g. Renal ultrasonography revealed bilateral echogenicity. His serology revealed a positive IgM for M. pneumoniae. The nasopharyngeal polymerase chain reaction was positive for rhinovirus. Blood and urine cultures were negative. Treatment with azithromycin resolved the hematuria within 1 week. Follow-up showed mild residual hematuria, and the patient remained under observation. CASE 2 A 4-year-old male was initially hospitalized for hyponatremia and fever (39.5 °C), treated with intravenous fluids, and discharged. Two days later, he developed macroscopic hematuria. At presentation, he was afebrile with normal blood pressure and no edema. Laboratory analyses showed a total leukocyte count of 7.84 x 103/μL, neutrophils 5.14 x 103/μL, platelet count of 371,000/mm3, hemoglobin 10.9 g/dL, g/dL, urea 19 mg/dL, creatinine 0.48 mg/dL, and albumin 45 g/L, C-reactive protein 8.9 mg/L. Antistreptolysin O was 180 IU/mL. Complement factors C3 was 1.15 mg/dL, and C4 was 0.15 mg/dL, within the normal range. Urinalysis revealed 919 red blood cells per high-power field, with a microalbumin-to-creatinine ratio of 174 mg/g. Polymerase chain reaction was positive for rhinovirus, and anti-Mycoplasma IgM was also positive. Blood and throat cultures were negative. Azithromycin was administered, and hematuria resolved within 7 days. Urine analysis normalized, and the patient was scheduled for follow-up. These cases illustrate how co-infections of M. pneumoniae and rhinovirus can lead to renal complications in children, with hematuria being a prominent feature. Immune-mediated mechanisms, including immune complex deposition, likely played a role in these patients' glomerular inflammation, consistent with previous reports of M. pneumoniae–associated glomerulonephritis and IgA nephropathy.1–5 Azithromycin, a macrolide antibiotic, resolved symptoms quickly in both cases, underscoring its efficacy in managing M. pneumoniae infections.2,4 Although rhinovirus is usually managed with supportive care, the coinfection appeared to exacerbate renal involvement, requiring close monitoring.6,7 These cases are consistent with literature suggesting that viral and bacterial coinfections can trigger immune responses leading to renal complications, including glomerulonephritis. Close observation and early intervention are critical in preventing long-term damage. Co-infections of M. pneumoniae and rhinovirus can result in significant renal complications in children. Early diagnosis and treatment with antibiotics like azithromycin, coupled with close follow-up, are essential to prevent long-term renal sequelae.