Legionella pneumonia with severe rhabdomyolysis

A 41-year-old man presented with a 5-day history of fever, non-productive cough and shortness of breath associated with copious watery diarrhoea and excessive fatigue. Apart from heavy smoking and alcohol misuse, there was no significant past medical history including no recent travel.

On examination, we found the patient to be diaphoretic, tachycardic (144 beats/min) and tachypnoeic (42 breaths/min), with a temperature of 39.7°C and blood pressure of 155/105 mmHg. He had an oxygen saturation of 98% after 8 L/min of supplemental oxygen. Auscultation of the chest elicited coarse crepitations over the right lung base and normal heart sounds. He had generalised weakness but no focal neurological deficit.

Laboratory results on admission showed a sodium level of 126 mmol/L (reference interval [RI], 137–145 mmol/L); chloride level, 96 mmol/L (RI, 100–109 mmol/L); potassium level, 3.3 mmol/L (RI, 3.5–4.9 mmol/L); urea level, 10.7 mmol/L (RI, 2.7–8.0 mmol/L), rising to a peak of 46.5 mmol/L; and creatinine concentration 310 μmol/L (RI, 50–120 μmol/L), rising to a peak of 908 μmol/L. Liver function test results were moderately abnormal: aspartate transaminase, 471 U/L (RI, < 45 U/L; peak, 860 U/L); alanine transaminase, 200 U/L (RI, < 55 U/L; peak, 1309 U/L); and lactate dehydrogenase, 4379 U/L (RI, 110–230 U/L). There was leucocytosis, with a white blood cell count of 13.6 × 10⁹/L (RI, 4.0–11.0 × 10⁹/L), neutrophilia (87.1%), mild thrombocytopenia (platelet count, 114 × 10⁹/L (RI, 150–400 × 10⁹/L) and an elevated C-reactive protein level (360 mg/L, RI, < 10 mg/L).

The patient’s serum creatine kinase (CK) level was elevated to 89 860 U/L (RI, < 250 U/L) and his serum myoglobin level was 42 268 μg/L (RI, < 85 μg/L). CK levels peaked at 141 116 U/L on Day 3.

On admission, the patient’s chest x-ray showed right middle lobe consolidation. His renal ultrasound was unremarkable. Subsequently, a sputum culture grew Legionella pneumophila serogroup 1. Urinary antigen test results were also positive for this organism, further confirmed by serology (antibody titre of 1 : 128).

The patient was admitted to the intensive care unit and treatment commenced with ceftriaxone 2 g (stopped after serological confirmation of Legionella) and azithromycin 500 mg daily (continued for 14 days). He was oligoanuric and required haemodiafiltration, which improved urine output along with renal functions. The principal cause for his renal failure was postulated to be severe rhabdomyolysis. Although dehydration related to diarrhoea may have been contributory, it was not deemed to be the main cause of renal failure since the patient was never hypotensive during admission. He was discharged from hospital after 20 days, with normal electrolyte levels and near-normal renal function.

Postinfection rhabdomyolysis is a rare complication associated with Legionella, first described in 1980.1 The mechanism of rhabdomyolysis associated with Legionella infection is unknown. Theories include direct invasion of Legionella into the muscle itself, or release of its endotoxin into the circulation with subsequent muscle injury.2

A literature review identified only 23 cases of rhabdomyolysis associated with Legionella infection. Most cases were from non-English publications, which could not be adequately translated, limiting data extraction. A CK level increase of > 50 000 U/L was identified in only seven of the 23 patients (Box).3-9 A marked predominance of male sex was observed. All patients underwent dialysis except one, who was managed with intravenous mannitol and forced alkaline diuresis,3 but all survived.

In conclusion, while a moderate increase in CK concentration is common with Legionella infection, marked rhabdomyolysis with CK levels > 50 000 U/L leading to acute renal failure is rare. To our knowledge, this is the first case report of L. pneumophila from Australia with this association. Clinicians should be aware of this possible complication and maintain a high index of suspicion, since early recognition and prompt treatment will prove lifesaving.