Q-uestioning the Diagnosis: An Educational Case Report

Area of Science:

• Nephrology
• Infectious Diseases
• Immunology

Background:

• Q fever, a zoonotic infection caused by Coxiella burnetii, can lead to renal injury but is rarely considered in the initial differential diagnosis of glomerulonephritis.
• Delayed diagnosis of Q fever can result in prolonged morbidity and suboptimal patient outcomes.

Observation:

• A 52-year-old female presented with symptoms suggestive of glomerulonephritis, including rash, joint pain, hematuria, and elevated creatinine.
• Kidney biopsy revealed immune complex mesangial proliferative glomerulonephritis, initially presumed to be lupus nephritis due to clinical presentation.
• The patient exhibited an atypical response to immunosuppressive therapy, remaining steroid-dependent with recurrent flares.

Findings:

• Further investigation revealed positive Q fever serology, leading to a diagnosis of chronic Q fever with renal involvement.
• Treatment with doxycycline and hydroxychloroquine resulted in symptom resolution, normalization of renal function, and disappearance of hematuria.
• Cessation of therapy led to a rise in Q fever IgM titers, necessitating indefinite retreatment.

Implications:

• This case underscores the importance of maintaining a broad differential diagnosis, particularly in cases with atypical clinical features or treatment responses.
• It highlights that clinical improvement with immunosuppressants does not exclude an underlying infectious etiology for glomerular disease.
• Considering infectious causes like Q fever in the differential diagnosis of glomerulonephritis is crucial for timely and effective management.