CDT Dermatologic Conditions & Diseases 3 — Questions and Answers
Question 1: Erythema chronicum migrans, the hallmark rash of Lyme disease, is caused by which organism?
- Treponema pallidum
- Borrelia burgdorferi (Correct answer)
- Rickettsia rickettsii
- Bartonella henselae
Correct answer: Borrelia burgdorferi
Borrelia burgdorferi, transmitted by Ixodes ticks, causes the expanding annular 'bull's-eye' rash of Lyme disease known as erythema migrans.
Question 2: A patient with HIV presents with violaceous nodules on the lower extremities. Which diagnosis should be considered first?
- Bacillary angiomatosis
- Kaposi sarcoma (Correct answer)
- Pyogenic granuloma
- Blue rubber bleb nevus
Correct answer: Kaposi sarcoma
Kaposi sarcoma, associated with HHV-8, presents as violaceous macules, plaques, or nodules and is strongly linked to HIV/AIDS.
Question 3: Necrobiosis lipoidica is most commonly associated with which systemic condition?
- Thyroid disease
- Inflammatory bowel disease
- Diabetes mellitus (Correct answer)
- Lupus erythematosus
Correct answer: Diabetes mellitus
Necrobiosis lipoidica is strongly associated with diabetes mellitus, presenting as yellowish-brown plaques on the shins.
Question 4: What is the Koebner phenomenon?
- Psoriasis flare triggered by stress
- Development of skin lesions at sites of trauma in susceptible individuals (Correct answer)
- Spontaneous resolution of skin lesions
- Spread of infection through scratching
Correct answer: Development of skin lesions at sites of trauma in susceptible individuals
The Koebner (isomorphic) phenomenon refers to the appearance of skin lesions characteristic of a disease at sites of cutaneous trauma, seen in psoriasis, vitiligo, and lichen planus.
Question 5: Which subtype of rosacea is characterized primarily by persistent facial erythema and telangiectasia without papules or pustules?
- Phymatous rosacea
- Ocular rosacea
- Papulopustular rosacea
- Erythematotelangiectatic rosacea (Correct answer)
Correct answer: Erythematotelangiectatic rosacea
Erythematotelangiectatic rosacea (subtype 1) presents with central facial flushing, persistent erythema, and visible blood vessels without inflammatory lesions.
Question 6: A patient presents with thick, hyperkeratotic skin on the palms and soles from birth. Which hereditary condition does this suggest?
- Ichthyosis vulgaris
- Palmoplantar keratoderma (Correct answer)
- Darier disease
- Hailey-Hailey disease
Correct answer: Palmoplantar keratoderma
Palmoplantar keratoderma (PPK) is a group of hereditary disorders characterized by diffuse or focal thickening of the skin on palms and soles.
Question 7: Dermatitis herpetiformis is associated with which underlying condition?
- Crohn's disease
- Celiac disease (gluten-sensitive enteropathy) (Correct answer)
- Ulcerative colitis
- Primary biliary cirrhosis
Correct answer: Celiac disease (gluten-sensitive enteropathy)
Dermatitis herpetiformis is the cutaneous manifestation of celiac disease, caused by IgA deposits at the dermal-epidermal junction, presenting with intensely pruritic vesicles.
CDT Dermatologic Conditions & Diseases 3
Erythema chronicum migrans, the hallmark rash of Lyme disease, is caused by which organism?