Arthritis associated with Mycoplasma pneumoniae in a pediatric patient: A case report

INTRODUCTION: Mycoplasma pneumoniae (MP) infection in infants is usually overlooked and it might result in important complications if left untreated. MP-induced arthritis is probably the least common extrapulmonary manifestation and frequently leads to delays in the diagnosis. PATIENT CONCERNS: We report the case of a 2-year-old female child admitted in our clinic for prolonged fever (onset 2 weeks before the admission), for which the general practitioner established the diagnosis of acute pharyngitis and recommended antibiotics. But the fever persisted and the patient was referred to a pediatrician. DIAGNOSIS: The laboratory tests revealed leukocytosis with neutrophilia, elevated C-reactive protein and liver cytolysis. The blood and urine cultures, as well as the serological hepatitis B and C, toxoplasmosis, Epstein Barr virus, Rubella, Herpes virus, and cytomegalovirus were negative. The chest X-ray established the diagnosis of pneumonia. The fever persisted for approximately 2 weeks after admission. On the 2nd week of admission, the patient began to experience gait difficulties complaining of pain in the right hip and ankle. The cardiology and pneumology consults revealed no pathological findings. The evolution was favorable after the initiation of Levofloxacin and MP infection was detected as we suspected. Moreover, the ultrasound of the hip revealed a mild joint effusion, while the ankle joint appeared to be normal at ultrasound. Thus, we established the diagnosis of hip and ankle arthritis based on the clinical and ultrasound findings. INTERVENTIONS: Levofloxacin by vein was continued for 5 days, replaced afterwards with clarithromycin orally for 2 weeks. OUTCOMES: The gait difficulties persisted for approximately 5 months from the initial diagnosis, and improved once the titer of immunoglobulin M anti-MP antibodies lowered considerably. After more than 8 months, the patient was completely asymptomatic and the immunoglobulin M anti-MP was close to the normal range. CONCLUSION: The awareness of MP-induced arthritis in children represents the cornerstone in preventing diagnostic delays and initiating the proper treatment.