annular and scaling eruptions (papulosquamous)

Question 1

Tinea corporis etiology

Answer 1

“ringworm”
but actually a fungal infection - dermatophytosis
most often caused by Trichophyton rubrum, or
Microsporum canis if exposed to animals

Question 2

Tinea corporis histology

Answer 2

hyperkeratosis and parakeratosis
numerous inflammatory cells in the dermis and the epidermis
sparse fine branching hyphae

Question 3

Tinea corporis clinical features

Answer 3

annular scaling edge
well-demarcated plaques
central clearing
single or multiple lesions
usually asymmetrical

Question 4

Tinea corporis dx

Answer 4

scrape scale edgings for KOH and culture

PAS stain shows fungal hyphae

Question 5

Tinea versicolor etiology

Answer 5

also called pityriasis versicolor
caused by Malassezia furfur or pityrosporum versicolor
Common in young adults
risk factors: warm, humid climate, oily skin, hyperhidrosis

Question 6

Tinea versicolor histology

Answer 6

hyperkeratosis without parakeratosis
minimal inflammation
numerous yeast and plump hyphae (sausage and meatballs)

Question 7

Tinea versicolor clinical features

Answer 7

well-marginated round scaling hypo- or hyperpigmented macules

Question 8

Tinea versicolor dx

Answer 8

positive KOH microscopy or scale with “spaghetti and meatballs” spores and hyphae
DDx vitiligo, pityriasis alba, post-inflammatory hypopigmentation

Question 9

Secondary syphilis etiology

Answer 9

2-6 months after primary syphilis
may/may not have hx of painless chancre
caused by treponema palladium

Question 10

Secondary syphilis clinical features

Answer 10

Look for involvement of palms and soles.
First eruption is macular then can be papulosquamous, pustular, or acneiform.
Chondylomata lata: flat-topped papules in moist areas (mouth, urogenital)

Question 11

Secondary syphilis dx

Answer 11

serological testing or skin biopsy