Contributed by Melina Flanagan, MD, MSPH, Casmiar Nwaigwe, MD, and William Pasculle, ScD
Published on line in July, 2004
An african american male in his 50s presented to the Emergency Room with intractable pain of the left lumbar region that radiated down his leg. He had a 14-year history of chronic back pain due to an industrial injury normally kept under control with Ibuprofen, 800 mg tid. Three days prior to admission, however, his back pain became much worse than usual until it reached a 10/10 severity, and was not relieved by Ibuprofen. . Three months prior to this admission, he suffered Streptococcus pneumoniae pneumonia and bacteremia, which were treated successfully with cefuroxime, azithromycin, and levofloxacin.
The patient was afebrile. On examination, he had a positive left-sided straight leg raise. His white blood cell count was 6.7 x106/mm3 (3.8-10.6) (69% neutrophils, 12% lymphocytes, and 19% monocytes), hemoglobin and hematocrit were 8.9g/dL and 27.6%, and his platelets were 258 x106/mm3 (156-369). His erythrocyte sedimentation rate was elevated at >150. His IgG was 4,440 mg/dL (751-1,560), IgA was 20 (82 - 453), and IgM was <25 (42-74). C-reactive protein was 2.8 mg/dL (0-.744). His chemistry profile was within normal limits.
An MRI of the lumbosacral region was performed (Figure 1). It demonstrated a peripherally enhancing multiloculated collection within the left paraspinal musculature (psoas) extending from the L4-5 level to the top of S1. The largest loculation was 4.7 x 2.8 x 1.7cm. There was no evidence of epidural extension or osteomyelitis.
The patient was admitted to the hospital, and Interventional Radiology performed ultrasound-guided drainage of about 12 cc of grossly purulent material from the abscess. A Gram stain of the purulent material demonstrated Gram positive cocci in chains and pairs (Figure 2). While awaiting identification of the organism, he was treated empirically with ampicillin/ sulbactam, 1.5 gm iv q6h for a day and then vancomycin 1gm iv q12h.
Cultures and gram stain of both blood and the drained abscess material demonstrated the same organism.
Figure 2: Gram stain of abscess smear
Figure 3: Colonies from Sheep's blood agar plate
Streptococcal pneumoniae is a Gram positive cocci arranged in chains and pairs. On blood agar plates, colonies are surrounded by a green alpha-hemolytic zone (due to production of pneumolysin which breaks hemoglobin into a green pigment). Optichin disks, which contain a quinine derivative, selectively inhibit the growth of S. pneumoniae on blood agar plates, and are used to differentiate pneumococcus from other viridans streptococci .
Susceptibility testing of the isolate revealed that it was sensitive to levofloxacin, erythromycin, tetracycline, sulfamethoxazol, chloramphenicol, and vancomycin. The MIC for penicillin and ceftriaxone were 0.023 µg/mL and 0.016 µg/mL, respectively.
This patient's recurrent Streptococcus pneumoniae bacteremia, as well as his hyper-IgG, hypo-IgA and IgM prompted a search for an underlying immune disorder.
Upon identification of the Streptococcal pneumoniae, the patient was placed on ceftriaxone 2g iv q24 for 4 weeks and then p.o. for an additional 2 weeks. Repeat blood cultures on day 3 were negative. A transthoracic echocardiogram, performed to rule out endocarditis as a possible source of his bacteremia, showed no vegetations. On day 6 of his hospital stay he still had severe low back pain and repeat MRI showed re-accumulation of the fluid in his left paraspinal musculature. He had a pigtail catheter placed by Interventional Radiology that drained another 10 cc of purulent fluid. Drainage ceased over the next few days, and the pigtail drain was pulled out 5 days later.
Upon further work-up, the patient was HIV negative by serology. His C3 was 102 mg/dL (79-152) and C4 was <10. IgG subclass quantification demonstrated:
|Subclass||Patient value (mg/dL)|
Serum protein electrophoresis (Figures 4 and 5) showed a monoclonal gammopathy, with a spike of 2.39 g/dL and a total protein of 8.4 g/dL (6.0-8.3). Serum immunofixation (Figure 6) identified the monoclonal protein as an IgG kappa.