Clinical Problem: The Patient with an Active Rheumatic Disease
Make sure the “punishment” fits the “crime.”
Comment: One of the fundamental principles of rheumatology is to make certain that the intensity of treatment matches the severity of the disease. Pleuritis, arthralgia, and low-grade fever with systemic lupus erythematosus (SLE) will respond to 60 mg of prednisone given daily. But these manifestations will also respond generally to far less prednisone, eg, 10–20 mg daily, doses associated with a much lower risk of infection or other complications. In contrast, severe hemolytic anemia and glomerulonephritis in SLE may not respond to low-dose prednisone and often must be treated not only with high doses of prednisone but also additional agents.
Clinical Problem: Supplemental Therapy for the Glucocorticoid-Treated Patient WHO Is Stressed by Serious Illness or Major Surgery
A normal cosyntropin stimulation test excludes adrenal insufficiency induced by glucocorticoid therapy.
Comment: The cosyntropin stimulation test determines the ability of the adrenal gland to produce cortisol in response to an exogenous corticotropin (adrenocorticotropic hormone, ACTH). However, the endogenous response to stress requires that all components of the hypothalamic-pituitary-adrenal axis be intact. Individuals treated currently with glucocorticoids and for many months after such therapy can have insufficiency of the central components of this axis (ie, normal adrenal response to exogenous ACTH but subnormal ability to produce ACTH endogenously).
Because tests of the central components of the axis are complex, most authorities recommend empiric hydrocortisone supplementation (100 mg three times daily) when these patients face major surgery or the stress of serious medical illness. Once the patient is beyond the perioperative period, the baseline prednisone dose can be resumed.
Clinical Problem: Fever in the Patient with Rheumatic Disease: Underlying Disease or Superimposed Infection
Rheumatoid arthritis rarely causes high-grade fever.
Comment: Although low-grade fevers in the range of 37.5°C often accompany active rheumatoid arthritis (RA), high-grade fevers are rare. Only 5% of cases manifest fever >38°C, and less than 1% have temperatures >38.3°C. Therefore, high-grade fever in a patient with well-established RA should prompt an investigation for an underlying cause (eg, infection) other than RA. In a patient with the new onset of inflammatory arthritis, the presence of high-grade fever is an argument against the diagnosis of RA or even a complication of RA, such as rheumatoid vasculitis (see Chapter 42). (See Chapter 4 for a discussion of the differential diagnosis of fever and arthritis).
Flare of a single joint in a patient with RA signals serious concern about septic arthritis.
Comment: Most flares of RA are polyarticular. When signs of new, increased inflammation affect only one joint, infection should be strongly considered. The most common cause of septic arthritis in RA is Staphylococcus aureus. Absence of fever does not exclude infection because only 50% of patients with septic arthritis present with fever. In the patient who has RA with only one “active” joint, arthrocentesis should be performed to exclude infection before intensifying anti-inflammantory therapy.
Always consider tuberculosis when a febrile illness develops in a patient treated with an anti–tumor necrosis factor agent.
Comment: Because tumor necrosis factor-α (TNF-α) is required for an intact host immune response to Mycobacterium tuberculosis, treatment with anti–TNF-α agents greatly increases the risk of tuberculosis. Although infliximab has been most closely associated with the greatest risk of tuberculosis in studies, the risk is likely a class effect shared by all anti–TNF-α agents. Most cases, caused by reactivation of infection, have developed within weeks of starting anti–TNF-α therapy. There is almost certainly an increased risk of disease from primary exposure as well, however.
In the setting of anti–TNF-α therapy, tuberculosis can be acute, is often disseminated or extrapulmonary, and has an atypical histopathology (TNF-α is required for granuloma formation). Anti–TNF-α therapy also carries an increased risk of infection with other intracellular pathogens, including Listeria monocytogenes, and fungi, such as Histoplasma capsulatum and Coccidioides immitis.
When trying to distinguish between infection and active disease in a patient with SLE, the presence of rigors favors infection.
Comment: One of the great quandaries of hospital medicine for patients with SLE is determining whether an acute change is caused by infection or a flare of the disease. The presence of rigors clearly favors infection. Other clues may come from the complete blood count: many patients with SLE have a baseline tendency toward neutropenia (particularly lymphopenia) and thrombocytopenia. Elevations in either of these two blood counts raises the likelihood of infection.
Fever that develops in a patient with SLE treated with high-dose glucocorticoids is due to infection until proven otherwise.
Comment: Infection is a leading cause of morbidity and mortality in SLE, particularly in the setting of immunosuppression with high-dose glucocorticoids. Although SLE itself can cause fever >39°C, fever due to SLE most often occurs in the setting of clinically active disease (particularly serositis) and usually responds to glucocorticoid therapy. Fever that develops after high-dose glucocorticoids have been started should be attributed to SLE only after a vigorous search for infectious causes, including opportunistic infections.
When a patient with SLE remembers the precise hour that the disease “flared,” the patient more likely has an acute infection.
Comment: Most flares of SLE develop over days or weeks. Infections tend to present more abruptly. Therefore, a patient who says, “my disease flared at 10 o’clock” probably has an infection.
Apparent “flares” of rheumatic disease that occur while the patient is taking cyclophosphamide are almost always caused by a superimposed opportunistic infection rather than by activation of the underlying disease.
Comment: Over the last 25 years at one large medical center, not one patient transferred to that center because of “refractory vasculitis” has had active vasculitis: every one of the transferred patients has had an opportunistic infection.
Clinical Problem: The Patient with Acute Monarthritis
Acute monarthritis has three major causes: trauma, infection, and microcrystalline disease.
Comment: In the absence of trauma, acute monoarthritis usually means that the patient has an infection or has gout or pseudogout. Although crystal-induced arthritis is more common, it is critical not to overlook septic arthritis. Delay in the treatment of joint infections increases morbidity and mortality substantially.
The wrist and knee are to pseudogout what the great toe and foot are to gout.
Comment: The most commonly affected joints in gout are the great toe and other sites of the foot. Pseudogout in contrast most commonly affects the wrist and the knee.
Monarthritis of the knee is the most common articular manifestation of chronic Lyme arthritis.
Comment: In regions where Ixodes complex ticks and Borrelia burgdorferi are endemic, an individual with chronic, unexplained inflammation of the knee (synovial fluid negative for crystals and organisms) may have Lyme disease. Knee effusions due to Lyme disease can be intermittent.
Arthrocentesis is the diagnostic procedure of choice for the patient with unexplained, acute monoarthritis.
Comment: Analysis of synovial fluid allows the physician to answer three questions: Is the joint inflamed? Is infection present? Is crystal disease present? The synovial fluid white blood cell (WBC) count is the best single discriminator between inflammatory (>2000 WBC/mcL) and noninflammatory (<2000 WBC/mcL) arthritis. In cases of nongonococcal septic arthritis, examination of synovial fluid by Gram staining has limited sensitivity (approximately 50%), but culture of the synovial fluid is positive in >90%. Polarized light microscopy is a sensitive and specific test for the presence of urate and calcium pyrophosphate dihydrate crystals in synovial fluid.
Synovial fluid should be tested for glucose level.
Comment: Synovial fluid glucose levels tend to be low when there is intense inflammation, especially when the joint is infected. The synovial fluid WBC count, however, is a far better measure of the severity of joint inflammation. The synovial fluid glucose level adds nothing to what is learned from the synovial fluid WBC count and should not be ordered. When the diagnosis is in question, synovial fluid should always be sent for the three Cs: cell count, culture, and crystals.
The serum uric acid is a reliable test for the presence or absence of gout in the patient with acute monarthritis.
Comment: The serum uric acid level neither establishes nor refutes the diagnosis of acute gout. Gout develops in most patients after years of hyperuricemia, but it is not uncommon for the serum uric acid level to fall to within the normal range at the time of an acute attack. Determining the serum uric acid has some value in that a low level makes gout quite unlikely. A high serum uric acid level increases the probability of gout but is not definitive; asymptomatic hyperuricemia is common and can be present in patients with acute arthritis unrelated to gout. The definitive test for the diagnosis of acute gout is demonstration of intracellular urate crystals in synovial fluid from the affected joint.
Clinical Problem: The Patient with Acute Gout
Gout has never killed a single patient. Not so its treatment.
Comment: Imprudent or improper use of gout therapies can be associated with a host of serious and even fatal complications. Gout should be treated, but treated wisely by informed clinicians mindful of the patient’s entire clinical status. See the comments below on the potential dangers of specific gout treatments.
Intravenous colchicine is a first-line therapy for acute gout.
Comment:
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