IgAN and Acute Tubular Injury with Legionella

Acute kidney injury in the setting of Legionella pneumonia.

This biopsy is a middle-aged person with Legionella pneumonia who developed acute kidney injury. Early in the hospitalization, the baseline creatinine was 1.0 mg/dl. However, the creatinine rose to 6.5 over 5 days and Nephrology was consulted. Urinalysis showed microscopic hematuria and 2+ proteinuria. The creatinine increased to 7.5 and a biopsy was done. Serologic studies were ordered and were pending at the time of biopsy.

The images provided show a combination of acute tubular injury (Image 1), mild mesangial matrix expansion (Image 2) and mesangial IgA deposits (Image 3).

While the acute tubular injury likely represents a large portion of the patient’s acute renal failure, the mesangial deposits are less easily classified. The mesangial IgA deposits may represent primary IgA Nephropathy though there is no prior history of hematuria. IgA deposits may also be secondary to the ongoing, though under treatment, infection. Also, hidden or deep-seated infections such as infective endocarditis, visceral abscess, osteomyelitis etc. must be considered.