Native aortic valve endocarditis with Morganella morganii in a patient with multiple myeloma and valvular amyloidosis: a case report

BACKGROUND: Patients with multiple myeloma (MM) are known to be immune incompetent and experience higher incidences of infectious diseases. However, infective endocarditis (IE) is rarely observed in patients with MM and Morganella morganii (M. morganii) has rarely been associated with IE. CASE PRESENTATION: A 72-year-old female receiving 4th line treatment for MM presented with fever and concomitant confusion. Urinary culture revealed growth of Escherichia coli, wherefore broadspectrum penicillin and high-dose corticosteroids were initiated. However, blood cultures showed growth of M. morganii. Fluoroquinolone was added due to penicillin-resistance of the Morganella species. Two days after admission, the patient acutely deteriorated with hemodynamic instability. Gentamicin and high dose corticosteroids were added. Echocardiography showed marked aortic valve vegetation with severe aortic valve regurgitation, leading to the diagnosis of bacterial endocarditis of the native aortic valve. Shortly after diagnosis, the patient died. At autopsy, vegetation with gram-negative rods in the native aortic valve was observed, confirming the diagnosis of M. morganii-endocarditis. Additional staining for amyloid confirmed advanced light-chain (AL) amyloidosis with extensive amyloid depositions of the aortic valve and valvular damage as complications of her MM. CONCLUSIONS: Our case suggests that IE with M. morganii was facilitated by the combination of the cardiac amyloidosis with valvular impairment and the profound immune deficiency caused by the several chemo-immunomodulatory treatment lines and the MM itself. This case further illustrates that awareness for rare opportunistic infections in an era with growing potential of combined chemoimmunotherapy is warranted.