Dermatology MCQ - Viral Infections - Chikungunya fever

A 55-year-old woman presents with an abrupt onset of high fever, severe polyarthralgia, and a maculopapular rash. She recently returned from a trip to India. Physical examination reveals tenderness and swelling in the wrists, knees, and ankles. Laboratory studies show leukopenia and elevated inflammatory markers. Which of the following is the most likely causative agent and its primary vector?

A) Dengue virus; Aedes aegypti mosquito
B) Chikungunya virus; Aedes aegypti mosquito
C) Zika virus; Aedes albopictus mosquito
D) Plasmodium vivax; Anopheles mosquito
E) Rickettsia typhi; flea bite

Correct Answer: B) Chikungunya virus; Aedes aegypti mosquito

Explanation

This presentation is classic for chikungunya fever, an arboviral illness known for its severe and debilitating arthralgia.

Key Clinical Features of Chikungunya Fever:

• Acute Phase:

  • Abrupt onset of high fever (often >39°C).

  • Severe, symmetric polyarthralgia: Typically involves wrists, knees, ankles, and small joints of the hands. Joints are tender, swollen, and may be erythematous.

  • Maculopapular rash: Often truncal, can be pruritic.

  • Constitutional symptoms: Myalgia, headache, fatigue.

• Chronic Phase:

  • Persistent or relapsing arthralgia can last for months to years, mimicking rheumatoid arthritis.

• Laboratory Findings: Leukopenia, thrombocytopenia, elevated ESR/CRP.

Virologic and Transmission Features:

• Causative Agent: Chikungunya virus (an alphavirus, Togaviridae family).

• Vector: Primarily transmitted by Aedes aegypti and Aedes albopictus mosquitoes.

• Geographic Distribution: Tropical and subtropical regions (e.g., India, Africa, Southeast Asia, Caribbean).

Why Not the Other Options?

• (A) Dengue virus: Causes fever, rash, and arthralgia ("breakbone fever"), but arthralgia is typically less severe and not chronic. Dengue is more associated with hemorrhage/shock.

• (C) Zika virus: Causes mild fever, rash, and arthralgia, but not severe polyarthritis. Known for congenital microcephaly.

• (D) Plasmodium vivax: Causes malaria with fever and chills, but no polyarthralgia or rash.

• (E) Rickettsia typhi: Causes murine typhus (fever, headache, rash), but no arthritis. Transmitted by fleas.

Management:

• Supportive care: NSAIDs for pain and inflammation (avoid aspirin due to bleeding risk in possible co-infections like dengue).

• Chronic arthritis: May require DMARDs (e.g., methotrexate) in severe cases.

• Prevention: Mosquito avoidance (repellents, nets), no vaccine available.

Prognosis:
Acute symptoms resolve in 1-2 weeks, but chronic arthralgia affects ~30-40% of patients, significantly impacting quality of life.

Note: Chikungunya means "to become contorted" in the Makonde language, referring to the stooped posture from severe joint pain. Always consider chikungunya in travelers with fever and polyarthritis from endemic areas.