Is the Cause Benign or Potentially Dangerous?

Case 1: A 55-year-old truck driver who lives in the rural Midwest is hospitalized with fever, headache, poor appetite, a blanching rash, and diffuse pain. His illness began 6 days earlier with fever and aching in his joints. He then noticed small red spots on his forearms and legs that later spread to his trunk, palms, and soles.

He suspects he was exposed to poison ivy in the woods behind his home, where he keeps 10 dogs. His wife found a brown tick in his umbilicus a week earlier.

The patient has type 2 diabetes mellitus, which is controlled with glyburide. Temperature is 38.8°C (102°F); heart rate, 100 beats per minute; and respiration rate, 16 breaths per minute. Oral mucosa is dry. Generalized muscle tenderness is noted. Cardiac (except for tachycardia), pulmonary, abdominal, and neurologic findings are normal.

Laboratory results show a platelet count of 109,000/µL; low sodium (126 mmol/L); and elevated levels of serum aspartate aminotransferase (93 U/L), alanine aminotransferase (107 U/L), and creatine kinase (1423 U/L).

Which of the following conditions in the differential diagnosis do you suspect?

A. Allergic contact dermatitis

B. Ehrlichiosis

C. Rocky Mountain spotted fever

D. Lyme disease

E. Murine typhus

F. Scrub typhus

G. Secondary syphilis

H. Erythema multiforme

Case 1: The history of a tick bite followed by fever, myalgia, arthralgia, and a diffuse rash on palms and soles that spreads from the extrem-ities to the torso strongly suggests Rocky Mountain spotted fever (RMSF), C. The finding of hyponatremia, thrombocytopenia, and elevated transaminase levels in this patient further strengthened this presumptive diagnosis. An Ehrlichia chaffeensis titer of less than 1:32 ruled out ehrlichiosis. The patient's initial RMSF titer was 1:64, borderline positive for RMSF; at follow-up 3 months later, the Rickettsia rickettsii titer was 1:512 (normal, less than 1:32).

RMSF--the most frequently reported rickettsial disease in the United States--is usually transmitted to humans via a bite from an ixodid tick. Crushed tick fluids and tick feces can also harbor the bacteria. The American dog tick (Dermacentor variabilis) and the Rocky Mountain wood tick (Dermacentor andersoni) are the 2 main vectors. RMSF has a much wider distribution than the name implies. More than half of cases occur in the south Atlantic states. The highest number of reported cases are in North Carolina and Oklahoma.¹

Most cases occur between April and September, the period associated with increased numbers of adult and nymphal ticks. Persons exposed to wooded areas and possibly dogs in regions where the disease is endemic are at increased risk. Children younger than 10 years are particularly susceptible.

Initial symptoms are often nonspecific and include headache, fever, and arthralgia. Many patients seek treatment before the rash develops (typically 2 to 5 days after the fever starts). The nonpruritic, erythematous rash arises as small pink macules. The palms and soles are involved in about half of cases.²

Unlike the rash associated with RMSF, those of murine typhus and scrub typhus classically begin on the torso and spread to the extremities. Allergic contact dermatitis is pruritic, with few systemic manifestations. Lyme disease is typically associated with erythema chronicum migrans. Erythema multiforme is also characterized by a distinctive target lesion. Patients with secondary syphilis have a history of sexual contact with an infected person, a primary chancre, localized or diffuse macules on the trunk and proximal extremities, and lymphadenopathy.

More than half of patients with RMSF have a history of a tick bite. The diagnosis is usually suspected on clinical grounds. Treatment should never be delayed pending confirmation.

The usual treatment of RMSF is oral or intravenous doxycycline (100 mg bid for adults and children heavier than 45 kg). Use of alternative therapies, such as chloramphenicol and tetracycline, is limited by their side effects. Treatment is given for a minimum of 7 days and should exceed the febrile stage by 3 days. The greatest risk factor for a poor outcome is delay of treatment. Many fatal cases are associated with an atypical presentation (no rash) or delayed therapy.

In this patient, defervescence occurred within 48 hours of treatment, and myalgia and arthralgia decreased within 72 hours. At discharge, 1 week after admission, the rash had begun to fade. He had residual soreness of his palms and soles. *

(Case and photograph courtesy of Brett Mikeska, MD, and Sunil Patel, MD, of the University of Oklahoma Health Science Center, Oklahoma City.)

Case 2: A 30-year-old woman with systemic lupus erythematosus (SLE) and Raynaud phenomenon presents with fever (temperature up to 39.4°C [103°F]), rash, and generalized body aches of 1 week's duration. The rash--which arose on her face and spread to her hands, chest, and back--is asymptomatic. She denies exposure to sick persons and animals. Her medications include hydroxychloroquine and prednisone.

The patient's temperature is 38.3°C (101°F). Multiple erythematous, papulovesicular, blanching lesions cover her lips, cheeks, hands, chest, and back. No synovitis, arthritis, or joint effusions are noted. The erythrocyte sedimentation rate is 72 mm/h, and the level of white blood cell bands is elevated. A biopsy of a skin lesion is performed.

What is the most likely cause of this patient's symptoms?

A. Lupus-associated vasculitis

B. Stevens-Johnson syndrome

C. Polyarteritis nodosa

D. Pasteurella multocida infection

Case 2: Biopsy revealed superficial and deep inflammation with increased dermal mucin; these findings are consistent with lupus-associated vasculitis, A.

The cause of SLE is unknown. This disease is mediated by pathogenic autoantibodies and immune complexes that damage involved tissues.

Most cases of SLE occur in women, usually of childbearing age. In this patient, the diagnosis was made 7 years earlier, when she presented with photosensitivity, leukopenia, malar rash, oral ulcers, proteinuria, and a positive test for lupus anticoagulant.

The presentation of SLE varies widely because multiple systems may be involved. Vascular involvement may be caused by thrombi, which can affect vessels of any size. The thrombosis may result from underlying vasculitis or antiphospholipid antibodies. Thus, both immunosuppressant and anticoagulation therapies are appropriate.

In addition to lupus-associated vasculitis, the following conditions are in the differential diagnosis:

•Stevens-Johnson syndrome is characterized by high fever, extensive bullae and necrosis, and ulcers of the skin and orogenital mucosa--all of which were absent in this patient. Skin biopsy demonstrates subepidermal bullae with lymphocytic infiltrates in the perivascular areas.

•Polyarteritis nodosa has a progressive course with exacerbations and remissions, which this patient did not report. This is a necrotizing vasculitis of the small and medium-sized muscular arteries, typically the renal and visceral arteries; the presentation depends on which organs are involved. Some patients have purpuric skin lesions, biopsy of which reveals inflammation of the small blood vessels, particularly in the postcapillary venules.

•Infection caused by Pasteurella multocida--a Gram-negative coccobacillus--is usually related to contact with livestock, poultry, and domestic pets. Patients may complain of upper respiratory tract infection-type symptoms, with focal erythema, warmth, pain, and purulent discharge at the initial site of infection.

In this patient, MR angiography of the chest, abdomen, and bilateral upper extremities revealed no large vessel involvement. She was treated with enoxaparin, methylprednisolone, and hydroxychloroquine during her hospitalization. A tapering regimen of prednisone was prescribed at discharge, 1 week after admission. *

(Case and photographs courtesy of Stephanie Lacson, MD, Dan La, MD, and Daniel G. Arkfeld, MD, of the University of Southern California Medical Center, Los Angeles.)

Case 3: For the past week, a 6-year-old girl has had a low-grade fever, runny nose, and cough. The macular rash on her face developed the day before and rapidly spread to her shoulders and trunk.

What is your clinical impression?

A. Rheumatic fever

B. Epstein-Barr virus infection

C. Lyme disease

D. Erythema infectiosum

E. Rheumatoid disorder

F. Allergic hypersensitivity reaction

Case 3: This child has erythema infectiosum (fifth disease), D.Erythema infectiosum was named fifth disease when the classic infectious exanthemas were numbered first through sixth.

This common childhood exanthema is caused by human parvovirus B19, a nonenveloped, single-stranded DNA virus that replicates only in human erythrocyte precursors. The disease affects both sexes equally and is generally self-limited. Erythema infectiosum commonly occurs in late winter to spring in children aged 3 to 15 years; however, it can occur at any age. The incubation period (from viral acquisition to the onset of initial symptoms) is usually 4 to 14 days, but can be as long as 21 days. Infected persons are contagious before the rash appears. In most cases, spread is via respiratory droplets.

The prodromal phase often includes fever and symptoms of upper respiratory tract infection, followed by the exanthema, which begins with the classic "slapped cheek" appearance (first phase). Within 1 to 4 days, a macular or morbilliform eruption appears primarily on the trunk and shoulders (second phase); some patients may have pruritus. The exanthema fades in a lacy pattern and can recur for several weeks after the initial illness, when exacerbated by exercise, sun exposure, emotional stress, and heat (third phase).

Parvovirus B19 infection may manifest as an acute symmetric polyarthropathy in adults and can cause an aplastic crisis in patients with chronic hemolytic anemia. Transmission of the virus through the placenta can result in fetal anemia, congestive heart failure, hydrops fetalis, or stillbirth. Parvovirus B19 is also associated with other conditions, such as glove and sock syndrome, vasculitis, and glomerulonephritis.

The diagnosis is essentially clinical and is based on the patient's age and sex, the season, the distinct appearance of the rash, and the clinical course. When in question, the diagnosis can be established by testing for IgM-type parvovirus B19 titers. In this child, the results of this test showed the presence of IgM-specific antibody. Results of a rapid test for group A streptococci were negative.

The child's rash recurred for several weeks, when she was exposed to exacerbating factors; it eventually resolved without treatment. *

(Case courtesy of Bhagwan Das Bang, MD, of Opp, Ala. Photograph courtesy of Renee Lemaire, Mizell Memorial Hospital, Opp, Ala.)