A 79‐year‐old woman with longstanding MGUS presented to her primary MD with fatigue and was found to have anemia and renal failure. She was sent to the emergency department, where she was found to have a low‐grade fever, dense consolidation of Ihe right lung, and hypoxemia. She was admitted with a diagnosis of pneumonia. Her infection, anemia, and renal failure were thought to most likely represent a progression to symptomatic myeloma and a workup was initiated. The day following admission she was noted to have significant pallor and respiratory distress. Her Hb was 6.3 and room air oxygen saturation 76%. A repeat chest film showed progression of diffuse bilateral infiltrates. She was transferred to the intensive care and intubated for ARDS, attributed to multilobar pneumonia. She continued to worsen over days, requiring progressively higher PEEP and FiO2 support to maintain oxygenation. On a routine urinalysis sent for protein electrophoresis, 4 red cell casts were noted by the lab. Workup for a renal‐pulmonary vasculitic syndrome was initiated. A mini‐BAL was negative for evidence of alveolar hemorrhage. A renal biopsy was performed revealinc paud‐immune, focal, crescentic. glomerulonephritis. ANCA serology relumed positive in a perinuclear pattern. Methyl prednisolone and cyclophosphamide were administered for a diagnosis of microscopic panangiitis. She improved rapidly and was ultimately discharged home.
Monoclonal gammopathy is common, occurring in 5.3% of patients older than 70 years, with an estimated progression to myeloma of 1% per year. Despite its association with malignant lymphoproliferative disorders, it is also associated with autoimmune conditions. The patienl above also carried a longstanding diagnosis of interstitial lung disease (NSIP). This palient's serum free light chain levels were elevated, but the K/L ratio was preserved. This is also observed with chronic inflammatory diseases and older age. Although symptomatic myeloma predisposes bacterial infections including pneumonia, a renal‐pulmonary syndrome (ANCA+ vasculitis or anti‐GBM disease) explained this patient's clinical syndrome through one unifying diagnosis.
Symptoms potentially attributable to myeloma in the presence of a monoclonal gammopathy deserve consideration but should not limit a clinician's differential diagnosis — especially given the high prevalence of MGUS in the elderly. “Diagnostic anchoring“ is a common and potentially harmful cognitive error made by clinicians who delay or fail to consider alternate diagnoses due to a fixation in their initial clinical impression.
C. Hale, Nnone