Mr. G, aged 74, came to the ambulatory-care clinic initially for pain in his right shoulder and neck. The shoulder pain had started about one month earlier, when he developed a “grapefruit-sized” lump in the area, and was worse with movement. The patient denied fever, chills, and any associated trauma.

Two weeks later, after starting ciprofloxacin for a UTI secondary to methicillin-sensitive Staphyloccocus aureus (MSSA), the lump was a little smaller but still painful.

The patient’s neck pain had become severe four months before his visit. Past medical history included psoriatic and rheumatoid arthritis (RA) for more than 25 years.

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Mr. G denied tobacco or alcohol use and had no allergies. In addition to the ciprofloxacin, he was taking a “pain pill from Mexico for [his] arthritis.”


On examination, the patient was thin but alert and in no acute distress. Vital signs were BP 119/67 mm Hg, pulse 85 beats per minute, respiratory rate 18 breaths per minute, temperature 97.8°F. The neck exam showed a distorted profile (Figure 1) and limited range of motion. The right shoulder was swollen, warm, and tender, but without erythema. The patient had a large effusion with limited range of motion secondary to the pain. Mr. G also had “arthritis mutilans” of his hands (Figure 2). 

Cardiac examination revealed a regular heartbeat and no murmurs. Lungs were clear. No sensory or motor deficits were noted, but Mr. G was slightly unsteady on his feet. On his skin were scaly, erythematous, psoriatic plaques.


A complete blood count revealed a mild baseline anemia, felt to be anemia of chronic disease, but future colonoscopy was planned for colon cancer screening. The metabolic profile was normal. Erythrocyte sedimentation rate was 139 mm/hr and C-reactive protein was 10.5 mg/dL, both indicators of active inflammation. Synovial fluid aspirate was yellow and cloudy; WBC count was 52,000/µL, with 91% segmented neutrophils, RBCs 500/µL; no crystals were observed. Fluid culture grew out MSSA.

MRI of the neck showed marked spondylolisthesis of C1 in relation to C2, measuring approximately 11 mm. There was also evidence of basilar skull invagination with posterior and superior orientation of the dens axis resulting in severe foramen magnum stenosis as well as ventral indentation of the lower medulla at the cervicomedullary junction as a result of the dens position.


Following hospital admission, the orthopedic service performed incision and drainage of Mr. G’s shoulder. He was initially started on IV vancomycin and ceftriaxone but then switched two days later to nafcillin. In the search for a source of the MSSA, a transthoracic echocardiogram showed no vegetations; transesophageal echocardiography could not be performed. A CT scan of the abdomen and pelvis showed no abscess. An indium-111 scan did not reveal any other sites of abnormal leukocyte accumulation in the chest, abdomen, pelvis, or left shoulder suggestive of inflammation. Blood cultures were negative. 

Mr. G’s neck pain was due to an atlanto-axial subluxation in which the tip of the dens axis was in the foramen magnum and abutting the cervicomedullary junction; however, there was no evidence of myelopathy, paresis, or sensory deficits. The MRI showed us how serious this complication of RA can be.

Mr. G’s C1 vertebra and basilar skull were very close to his spinal cord, and we wondered whether the cord could be transsected. Alarm signs of spinal-cord damage in RA include severe neck pain, diminished motor power in the arms and legs, tingling in the fingers and feet, or disturbed bladder function, such as urinary incontinence or urinary retention. We were concerned that Mr. G’s unsteadiness was due to the spinal cord findings seen on MRI.

The neurosurgeon had an extensive discussion with Mr. G about the risks and potential benefits of any intervention. The patient knew that he had a serious problem in his upper cervical spine, but he did not want to take the chance of becoming quadriplegic from the surgery. He bravely and politely refused any surgical intervention.


Septic arthritis due to S. aureus can occur as a complication in any patient with RA. Patients with underlying arthritis who complain of acute pain in a single joint should have the joint aspirated and the synovial fluid sent for culture. Septic arthritis can cause a cloudy sometimes purulent exudate that usually contains >50,000 granulocytes/µL and reveals gram-positive cocci on the smear.

The presence of MSSA in the urine is always concerning for deep intravascular infection, so Mr. G was given antibiotics to cover for an occult hematogenous source. However, his clinicians suspected that Mr. G was colonized with MSSA, a fairly common occurrence with psoriasis. One recent study found S. aureus in >50% of psoriasis patients involved.


Six weeks of IV nafcillin administered through a peripherally inserted central catheter line for the MSSA right shoulder septic-joint infection yielded improvement of symptoms. The patient received the first 10 days of therapy in the hospital and the rest at home. To alleviate the effects of the atlanto-axial subluxation, he was given an Aspen cervical collar to use whenever he was out of bed. He was referred for follow-up in the neurosurgery clinic.

Dr. Dunn is assistant professor of internal medicine at the James A. Haley VA Medical Center in Tampa, where Dr. Mizrachi is a resident.

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  • Klippel JH, Dieppe P, Ferri FF. Primary Care Rheumatology. Philadelphia, Pa.: Elsevier; 1999:143-161.
    Tomi NS, Kränke B, Aberer E. Staphylococcal toxins in patients with psoriasis, atopic dermatitis, and erythroderma, and in healthy control subjects. J Am Acad Dermatol. 2005;53:67-72.