Infectious Disorders Flashcards
Where do dermatophytes survive and what is tinea manuum?
They infect and survive only on keratinized tissue (i.e. skin, hair, and nails) and thus fail to survive on mucosal skin which does not have a keratin layer
Tinea manuum = tinea of hands
Is tinea versicolor a dermatophyte infection?
No, it is caused by a yeast-like fungus called Malassezia furfur which is potentially more invasive than the dermatophytes.
Also called pityriasis versicolor
What might tinea capitis be confused with and how do you differentiate it from those entities?
Confused with psoriasis or seborrheic dermatitis, because it appears as a diffuse, fine, white adherent scale on the scalp
Differentiated by presence of “black dots” which are broken hair shafts, as well as hair loss, which is not typically seen in those other two conditions
What is kerion? What are the complications?
The boggy, inflamed, postular appearance of the scalp in a severe inflammatory response to tinea
Can lead to scarring and permanent hair loss. Often associated with lymphadenopathy
How is tinea capitis diagnosed and treated?
Diagnosed via KOH prep which shows spores in or around hairshaft
Treatment: oral griseofulvin or terbinafine is required
Adjunctive therapy with ketoconazole shampoo may be used
Who gets tinea corporis and how does it appear?
Typically pre-adolescents
“Ringworm” - Appears as an erythematous patch with raised, scaly borders. There is often a central clearing.
Who gets tinea cruris and what area is usually spared?
Usually in post-pubertal males who are sweaty and obese
It will be bilateral, advancing to thighs and buttocks, but usually spares the scrotum.
What is the most common tinea infection and what are the three subtypes, and which of these is most common?
Tinea pedis - “Athlete’s foot”
- Interdigital - most common, between toes
- Moccasin distribution - lateral borders of feet/soles
- Acute vesicular - difficult to differentiate from dyshidrotic dermatitis
What is the common presentation of tinea manuum?
Two feet, one hand:
Often presents secondary to pre-existing tinea pedis, as patches with fine scaling appear on palm of dominant hand due to touching tinea pedis.
What is tinea incognito? How does it appear?
It is tinea which looks abnormal due to misdiagnosis and usage of topical corticosteroids
- > rash flares with withdrawal of steroid
- > rash is often disseminated, lacking scale or raised border
What is tinea unguium also called, and what are the risk factors?
Onychomycosis
Risk factors: increasing age, immunosuppression, diabetes, poor circulation
How does tinea unguium appear and what is on the DDx?
Thickened, discolored nail plate with onycholysis (splitting apart) and subungual hyperkeratosis
DDx:
Psoriasis
Chronic trauma
How is tinea unguium diagnosed and treated?
Diagnosis: KOH prep, or nail clipping for PAS staining (Very quick but shows dead fungus). Gold standard is fungal culture.
Treatment: Long course (12 weeks) of oral terbinafine which is hepatotoxic, so rarely done
When does tinea versicolor usually happen and what parts of the body are favored?
Usually during the summer months (hot, humid weather) with high sebaceous gland activity
- > malassezia furfur loves oil / lipids
- > especially occurs in upper trunk and arms
Where in the skin does Malassezia furfur live, and what will the rash look like?
Lives in the stratum corneum, looks like small, circular hypopigmented (not depigmented like vitiligo) patches with fine scale
What does Malassezia furfur look like on KOH prep and what should the treatment be?
Spaghetti and meatball yeast and pseudohyphae forms
Treatment: Oral azoles, with recommendation to sweat 1 hour afterwards (increase sebaceous gland concentration), also selenium sulfide (Selsun blue)
What are the risk factors for candidal intertrigo?
Obesity, diabetes (think of candy jar in sketchy), pregnancy / OCPs (think of BCP in sketchy), antibiotic use (think of jar of pills in sketchy)
How does candidal intertrigo appear and what areas are involved?
Appears as moist, erythematous, macerated plaques in warm areas (skin folds)
Often pustules around periphery
Can be distinguished from dermatophyte infection via involvement of scrotum
What is angular cheilitis a possible presentation of in children? What can predispose children to it?
Oral candidiasis -> painful, red scaly macules and fissures on oral commissures
Children predisposed by lip-licking -> saliva forms a warm environment for candidal growth
How does primary HSV infection generally present in children?
Fever, malaise, regional lymphadenopathy, and gingivostomatitis.
May also allow for a secondary infection with S. pyogenes/aureus -> impetigo.
How does genital herpes tend to present?
Vesicles grouped on an underlying erythematous base, but they pop easily and tend to present as superficial erosions and ulcerations
What is herpetic whitlow and who gets it?
Herpes on fingers of kids who suck them, or healthcare workers
What type of HSV is associated with TORCH infections? What are the clinical manifestations?
HSV-2, passed via mucous membrane contact during delivery
Manifestations: meningoencephalitis, herpetic vesicular lesions which are widespread
