3. Skin Infections & Infestations

What is Folliculitis?

A superficial infection of the hair follicles (epidermis).

What is the most common pathogen causing Folliculitis?

Staphylococcus aureus.

What organism causes 'Hot Tub Folliculitis'?

Pseudomonas aeruginosa.

How does Folliculitis typically present clinically?

Multiple, small, scattered, erythematous papules or pustules surrounding a hair, often pruritic.

What is the treatment for mild Folliculitis?

Warm compresses TID, avoid shaving, and topical antibiotics (Mupirocin or Clindamycin).

Define a Furuncle ('Boil').

An infection of the hair follicle that extends through the dermis into subcutaneous tissue, forming an abscess.

Define a Carbuncle.

A coalescence of several furuncles forming a single inflammatory mass with purulent drainage from multiple follicles.

When are oral antibiotics indicated for Furuncles?

If the lesion is >2cm, multiple lesions exist, extensive cellulitis is present, or the patient is immunocompromised/has systemic signs of infection.

What are the two main types of Impetigo?

Non-bullous (70% of cases) and Bullous.

What is the hallmark clinical finding of Non-bullous Impetigo?

Honey-colored crusts.

Which pathogens cause Non-bullous Impetigo?

Staphylococcus aureus and Group A Beta-hemolytic Streptococcus (Strep pyogenes).

What is the first-line treatment for mild/localized Non-bullous Impetigo?

Topical Mupirocin TID and warm compresses.

What is Staphylococcal Scalded Skin Syndrome (SSSS)?

An exotoxin-mediated response causing rapid, tender exfoliation of the skin, primarily seen in infants and children <6 years old.

What is Nikolsky’s sign?

A finding where gentle stroking of the skin causes separation at the epidermis (seen in SSSS).

How is SSSS treated?

ICU admission, IV fluids, skin care, and IV antibiotics directed at S. aureus (Nafcillin, Oxacillin, or Vancomycin).

What differentiates Erysipelas from Cellulitis?

Erysipelas is a superficial infection with sharply demarcated, raised borders, whereas Cellulitis involves deeper tissue with poorly defined margins.

What is the most common pathogen causing Erysipelas?

Group A Beta-hemolytic Strep (S. pyogenes).

What are the hallmark symptoms of Toxic Shock Syndrome (TSS)?

Sudden high fever (>102°F), hypotension, confusion, and a diffuse 'sunburn-like' rash involving palms/soles.

What is a common historical risk factor for TSS in women?

Tampon use (or nasal packing/wound packing).

What is the recommended antibiotic regimen for TSS?

Clindamycin + Vancomycin + a Penicillin/Beta-lactamase inhibitor (e.g., Zosyn) or Cefepime.

What organism causes Strep Throat?

Streptococcus pyogenes (Group A Beta-hemolytic Strep).

What are the clinical features of Strep Throat (Centor Criteria)?

Sore throat, fever, exudative tonsillitis, tender cervical lymphadenopathy, and absence of cough.

What is the drug of choice for Strep Throat?

Penicillin V or Amoxicillin for 10 days.

What distinguishes Scarlet Fever from Strep Throat?

A 'sandpaper' rash (sparing palms/soles), strawberry tongue, and Pastia lines (petechiae in skin folds).

What are the potential complications of untreated Strep Throat?

Rheumatic Fever, Glomerulonephritis, Peritonsillar Abscess, Otitis Media, Mastoiditis.

What criteria are used to diagnose Rheumatic Fever?

The Jones Criteria (2 Major OR 1 Major + 2 Minor manifestations, plus evidence of preceding GAS infection).

List the 5 Major Manifestations of Rheumatic Fever.

1. Arthritis (migratory polyarthritis)

2. Carditis (pancarditis)

3. Sydenham chorea (involuntary movements)

4. Subcutaneous nodules

5. Erythema marginatum (rash).

What is the long-term sequela of Rheumatic Fever involving the heart?

Rheumatic Heart Disease (most commonly affecting the mitral valve).

What virus causes Erythema Infectiosum?

Parvovirus B19.

What is the classic clinical presentation of Fifth Disease?

A 'Slapped Cheek' appearance followed by a lacy rash on the body 1-2 days later.

Why is Parvovirus B19 dangerous in pregnancy?

It can cause fetal loss (hydrops fetalis) or severe anemia.

What is the drug of choice for Pediculosis (Lice)?

Permethrin (Elimite, Nix) topical.

What is the pathognomonic sign of Scabies?

The Burrow (a short, elevated, S-shaped track), often found in web spaces of fingers.

When is pruritus (itching) most severe in Scabies?

At night (nocturnal pruritus).

What is the standard treatment for Scabies?

Permethrin cream 5% applied to the entire body (neck down) for 8-14 hours, repeated in 1 week.

How do Bedbug bites typically appear?

Clusters of papules/wheals on exposed skin, often in a linear pattern.

Do Bedbug bites require medical treatment?

Usually no; symptomatic treatment with corticosteroid creams or oral antihistamines is sufficient.

What is a common clinical sign of Folliculitis?

Erythematous papules or pustules around hair follicles.

What is the primary treatment approach for Furuncles?

Incision and drainage may be necessary, especially for large abscesses.

What systemic signs may indicate a greater severity in Furuncles?

Fever and chills.

What is one preventive measure for Folliculitis?

Avoiding sharing personal items like razors.

What bacteria is commonly involved in Bullous Impetigo?

Staphylococcus aureus.

Which age group is primarily affected by Scalded Skin Syndrome?

Infants and children under 6 years old.

How quickly can SSSS progress for those infected?

Rapidly, often within days.

What is the appearance of a rash in Erysipelas?

Shiny and raised with well-defined borders.

What two conditions can chronic untreated Strep Throat lead to?

Rheumatic Fever and Glomerulonephritis.

How often should topical antibiotics be applied for Impetigo?

Three times a day (TID).

How does a doctor typically assess for TSS?

Clinical criteria based on symptoms and presentation.

What can the absence of a cough indicate in a patient with suspected Strep Throat?

It supports the diagnosis of Strep Throat.

Which exam finding is specific to Scarlet Fever?

Strawberry tongue.

What is a classic feature of Erythema Infectiosum in the early stages?

A red rash on the cheeks resembling a slapped appearance.

What potential complication can arise from Scabies if left untreated?

Secondary bacterial infections.

What surface should Permethrin be applied to for Scabies treatment?

The entire body from the neck down.

How soon after treatment should scabies itch be expected to resolve?

Typically within a week.

What is a key symptom of Toxic Shock Syndrome in addition to fever?

Hypotension.

What is a notable finding at physical exam in Rheumatic Fever?

Joint swelling and tenderness.

What type of rash is associated with Rheumatic Fever?

Erythema marginatum.

What is a hallmark symptom of Staphylococcal Scalded Skin Syndrome?

Tender exfoliation of skin.

What method is commonly used to treat severe Cases of Erysipelas?

Intravenous antibiotics.

What is a first-line treatment for Cellulitis?

Oral antibiotics if it's mild.

What does the presence of Pastia lines indicate?

Scarlet Fever.

What are two key laboratory tests to support the diagnosis of Strep Throat?

Rapid antigen detection test and throat culture.

What is a common feature of the rash in Erythema Infectiosum?

It appears lacy after the initial slapped-cheek appearance.

What characterizes the appearance of scabious burrows?

S-shaped tracks created by the mites.

What common mistake do individuals make regarding bedbug bites?

Assuming they do not need treatment when they are symptomatic.

What preventive measures can help control lice outbreaks?

Washing bedding and clothing in hot water.

What common pathogen is associated with impetigo?

Staphylococcus aureus.

Why is diagnosis important for Strep Throat?

To prevent potential complications from untreated infection.

What are the signs of a more severe case of Cellulitis?

Rapid spread of redness and swelling.

How can Scabies be commonly misdiagnosed?

For allergies or other rashes.

What is the typical duration of antibiotic treatment for Strep Throat?

10 days.

What is the overall goal of treating Erysipelas?

Eradicate the infection and prevent complications.

What would you observe in a patient with a severe episode of TSS?

Multi-organ dysfunction.

How does hydration status affect patients with SSSS?

They often require IV fluids due to fluid loss.

Which topical treatment is specifically indicated for Lice?

Malathion or Permethrin.

What is a primary differential when considering Erysipelas?

Cellulitis.

What can exacerbate the symptoms of Scabies?

Increased sweating or irritation.

What age group is most susceptible to Fifth Disease complications?

Pregnant women.

What are typical findings on a skin assessment for Impetigo?

Red sores that rupture and ooze.

Why is early treatment of TSS crucial?

To prevent severe complications and mortality.

What provides a distinct clinical pattern in Scarlet Fever?

Rash that feels like sandpaper.

What systemic manifestation can arise from untreated Rheumatic Fever affecting the heart?

Mitral valve disease.

What is a curious aspect of Scabies transmission?

It is easily spread through skin-to-skin contact.

Why are infants particularly vulnerable to SSSS?

Their skin barrier is thinner and more susceptible.

What complication can persistent untreated Bedbug infestations cause?

Sleep disturbances and anxiety due to bites.

What should be monitored in patients receiving treatment for SSSS?

Signs of dehydration and electrolyte imbalances.

How long can symptoms persist after Scabies treatment?

Up to several weeks post-treatment.

What diagnostic test can confirm Group A Strep infections?

Throat swab culture.

Which topical medications are effective against Scabies?

Lindane and Benzyl benzoate.

What is the importance of the Jones Criteria?

To diagnose rheumatic fever and guide treatment.

What can negative Nikolsky’s sign indicate in a patient?

It may suggest the absence of SSSS.

What is a unique feature of a furuncle compared to Folliculitis?

It extends into subcutaneous tissue.

What physical signs might suggest a patient has impetigo?

Lesions with honey-colored crusting.

What is a common misconception regarding the treatment of Bedbug bites?

That they require antibiotics.

What does the term 'herald patch' refer to?

A single large lesion often seen in conditions like pityriasis rosea.

What commonly affects patients with SSSS in terms of fluid balance?

Hypovolemia from fluid loss.

What is a critical aspect to consider for patients with Erysipelas?

Close follow-up to ensure resolution.

What indicates the need for IV antibiotics in a patient with cellulitis?

If the patient is unable to take oral medications.

How can Parvovirus B19 be transmitted?

Through respiratory secretions.

What does a history of recurrent strep infections suggest?

That a patient may be vulnerable to rheumatic fever.