Fever and Arthralgia after Caribbean Travel

A 45-year-old woman presents to an urgent care clinic with 3 days of high fever, severe polyarthralgia, and a maculopapular rash. She returned 4 days ago from a 2-week vacation in the Dominican Republic where she stayed in a beachfront resort. The fever spikes to 39.5°C daily and is only partially responsive to acetaminophen. The arthralgia is symmetric, involves both small and large joints, and is most severe in the morning with associated stiffness lasting over an hour. The rash appeared on the second day of illness and is pruritic, spreading centrifugally from the trunk to the extremities. The joint pain is debilitating, affecting her wrists, fingers, ankles, and knees, limiting her ability to walk or grasp objects.

She has no significant past medical history and takes no medications. She reports multiple mosquito bites during her trip despite using DEET-based repellent. She traveled to Punta Cana and Santo Domingo, with day trips to rural areas where she noted abundant standing water. She used DEET-based repellent during the day but was bitten frequently in the early morning and late afternoon. She recalls being bitten by mosquitoes with distinctive white markings similar to the one pictured. She slept in air-conditioned accommodations with screened windows but did not use a bed net. She did not take malaria chemoprophylaxis. Her travel companions are asymptomatic. She denies any history of arthritis, autoimmune disease, recent tick exposures, blood transfusions, tattoos, or intravenous drug use. She works as a graphic designer and has no occupational exposures to infectious diseases.

On examination, she appears uncomfortable and is holding her wrists and ankles gingerly. Vital signs: temperature 39.2°C, heart rate 102 bpm, blood pressure 118/76 mmHg, respiratory rate 16/min, oxygen saturation 98% on room air. Skin examination reveals a diffuse maculopapular rash on the trunk and extremities with sparing of the palms and soles; the rash is blanching, non-petechial, and consists of 2-5 mm erythematous macules and papules. Musculoskeletal exam demonstrates symmetric swelling and tenderness of the metacarpophalangeal joints, wrists, ankles, and knees with painful limited range of motion. There is mild periarticular edema and warmth over the affected joints without erythema. Passive movement elicits severe pain, but active range of motion is also limited by discomfort. There is no lymphadenopathy, hepatosplenomegaly, or meningeal signs.

Laboratory studies show leukopenia (white blood cell count 2.8 × 10³/µL) with relative lymphopenia, thrombocytopenia (platelet count 112 × 10³/µL), and mild elevation of transaminases (AST 68 U/L, ALT 72 U/L). Serum creatinine and inflammatory markers (C-reactive protein 12 mg/L, erythrocyte sedimentation rate 18 mm/hr) are within normal limits. Rheumatoid factor and anti-cyclic citrullinated peptide antibodies are negative. Serum uric acid is 4.2 mg/dL. Rapid diagnostic tests for malaria (blood smear) and dengue (NS1 antigen) are negative. Blood cultures show no growth at 48 hours. Urinalysis is normal without proteinuria or hematuria. Reverse transcription polymerase chain reaction (RT-PCR) testing for arboviruses is pending. Plain radiographs of the affected joints show only soft tissue swelling without erosions or joint space narrowing. Chest radiograph is clear.