Severe Rhabdomyolysis in a Child: A Rare Extrapulmonary Manifestation of Mycoplasma pneumoniae Infection

To the Editors: Mycoplasma pneumoniae is a common cause of acute respiratory illnesses, ranging from mild upper respiratory tract infections to more severe pneumonia.1 While primarily known for its pulmonary involvement, M. pneumoniae can also cause extrapulmonary manifestations affecting nearly every organ system. Among musculoskeletal complications, polyarthralgia and transient myalgia are relatively common, but rhabdomyolysis remains an exceedingly rare presentation.1 Rhabdomyolysis associated with M. pneumoniae has been reported sporadically in the literature, primarily in patients presenting with otherwise straightforward respiratory symptoms.2 The diagnosis can be challenging as patients may not initially report classic symptoms such as muscle pain or cramping. Most documented cases occur in adults, with only a few reports describing severe rhabdomyolysis in children.2–6 Here, we present a case of massive rhabdomyolysis in a child with M. pneumoniae–associated lower respiratory tract infection, highlighting the importance of maintaining a broad differential diagnosis to ensure timely and appropriate management. A 6-year-old girl presented with a 1-week history of fever, nasal discharge, cough, abdominal pain, nausea, vomiting and diffuse muscle pain. Intravenous fluid therapy was initiated due to vomiting, and her urine was observed to be tea-colored. The patient appeared lethargic, with a capillary refill time exceeding 2 seconds, tachycardia and hypotension. On physical examination, she was alert, with normal heart sounds, bilateral equal breath sounds with fine crackles and no hepatosplenomegaly. Diffuse peripheral edema in the lower extremities was noted. Laboratory tests revealed a normal complete blood count and normal renal function tests. However, liver function tests showed significantly elevated transaminase levels (aspartate aminotransferase: 1987 U/L, alanine aminotransferase: 692 U/L). Creatine kinase was markedly elevated at 90,284 U/L, and lactate dehydrogenase was 2434 U/L. Total protein and albumin levels were low at 34 and 24 g/L, respectively. Urinalysis revealed negative leukocyte esterase, positive hemoglobin, negative nitrite and positive protein. The chest radiograph revealed fullness in the left hilar region along with bilateral reticular infiltrations (Fig. 1) Cardiac markers showed elevated troponin I at 259 ng/L, and CRP was 10.4 mg/L. A respiratory polymerase chain reaction panel, including M. pneumoniae, and influenzae was negative. Echocardiography revealed no cardiac abnormalities.FIGURE 1.: Change in CK levels over days. CK indicates creatine kinase.Further investigations were conducted to clarify the etiology, including serological testing for Toxoplasma, EBV, CMV and M. pneumoniae. The serological tests confirmed M. pneumoniae infection, with IgM >200 and IgG 32.7. The patient was treated with isotonic fluid boluses for hypotension, and bicarbonate-containing hydration was initiated due to rhabdomyolysis. Empirical antibiotics, including cefotaxime, clindamycin and clarithromycin, were started. Following the confirmation of M. pneumoniae infection, treatment was continued with a macrolide antibiotic. With hydration and macrolide therapy, the patient’s creatine kinase levels showed a significant daily decrease (Fig. 2). Peripheral edema resolved, muscle pain diminished and the patient’s lower extremity mobility improved, with no residual gait difficulty. By the 10th day of macrolide therapy, the patient was fully recovered and discharged in good health.FIGURE 2.: Fullness in the left hilar region and bilateral reticular infiltration.This case highlights a rare complication of M. pneumoniae infection—rhabdomyolysis—which was successfully treated with appropriate hydration and macrolide therapy.