Week 49: Dermatology part 1

Certain host factors predispose to cellulitis. The elderly and immunocompromised individuals are at risk for more severe disease. Patients with diabetes, immunodeficiency, cancer, venous stasis, chronic liver disease, peripheral arterial disease, and chronic kidney disease appear to be at a higher risk for recurrent infection, owing to an altered host immune response. While other factors that affect host immunity such as concurrent intravenous or subcutaneous “skin popping” drug use predispose to development of infection, the risk factor that is most strongly associated with cellulitis is lymphedema (odds ratio [OR] = 71.2).

Varicella zoster virus (human herpesvirus 3) is the causative agent in both chicken pox and shingles. Herpes zoster shown in this patient occurs from reactivation of the varicella zoster virus that has been dormant in a dorsal root nerve ganglion since an episode of chicken pox. Most reoccurrences occur in elderly and immunocompromised patients. Prior to the onset of rash, patients experience tingling or hyperesthesia in the dermatome. Painful, vesicular lesions then appear on the skin along the distribution of the dermatome. Patients are considered infectious from 5 days before the appearance of the rash until 5 days after the appearance of the vesicles. Until the vesicles are crusted over, patients required airborne isolation (negative pressure room) with contact precautions for anyone entering the room.

The correct answer is anti-staphylococcal antibiotics. This patient’s presentation is concerning for Staph Scalded Skin Syndrome. Treatment is with anti-staph antibiotics as well as supportive measures, particularly fluid resuscitation since these patients are essentially treated like burn victims due to the skin sloughing.

Given his recent camping trip and rash around the distal extremities, this is concerning forRocky Mountain spotted fever (RMSF). The vast majority of patients with RMSF present with some type of rash which typically is noticed 2-5 days after the onset of fever and starts peripherally and spreads to the trunk. Frank petechiae do not develop until the 6th day or later and can be a sign of severe disease requiring more aggressive treatment. Treatment should be initiated as soon as possible and may be initiated based on clinical suspicion. Doxycycline is the most effective treatment.

Kaposi sarcoma is an opportunistic cutaneous neoplasm linked to human herpesvirus (HHV)-8 infection. HHV-8 is also referred to as Kaposi sarcoma-associated herpesvirus (KSHV). It is an AIDS-defining illness in patients older than 13 years old infected with human immunodeficiency virus (HIV). It is the most common AIDS-associated tumor in homosexual patients, but other at-risk populations include intravenous drug users, blood-transfusion recipients, hemophiliacs and children born to HIV-positive mothers. Lesions are classically multifocal and are in different stages of development: papules, nodules, macules. Small violaceous macules may merge to form large plaques. Extracutaneous sites are frequently involved, including the oral mucosa, gastrointestinal tract, lungs and lymph nodes. Despite its viral oncogenesis, it responds well to chemotherapy and radiation.

Patients infected with Rubella (A) often have a self-limited disease course with morbilliform rash, whereas congenital rubella has a higher mortality and can cause the “blueberry muffin” rash with purpuric lesions. Meningococcemia from Neisseria meningitidis (C) most commonly causes a petechial or purpuric rash. Additionally, patients with this condition are systemically ill and often exhibiting altered mental status, hemodynamic instability and rapid clinical deterioration. Tinea versicolor (D) is caused by the Malassezia fungal genus and characteristically causes a hypopigmented papular rash that is more notable in darker-skinned individuals.

Tinea infections are caused by dermatophytes and are classified by the involved site. The most common infections in prepubertal children are tinea corporis and tinea capitis, whereas adolescents and adults are more likely to develop tinea cruris, tinea pedis, and tinea unguium (onychomycosis). In the United States, tinea capitis (scalp) most commonly affects children of African heritage between three and nine years of age. Early disease can be limited to itching and scaling, but the more classic presentation involves scaly patches of alopecia with hairs broken at the skin line and crusting. Tinea capitis may progress to kerion, which is characterized by boggy tender plaques and pustules. Tinea capitis must be treated with systemic antifungal agents because topical agents do not penetrate the hair shaft. However, adjunct treatment with selenium sulfide shampoo or 2% ketoconazole shampoo should be used for the first two weeks because it may reduce transmission. For many years, the first-line treatment for Tinea capitis was griseofulvin because it has a long track record of safety and effectiveness. However, randomized clinical trials have confirmed that newer agents, such as terbinafine and fluconazole, have equal effectiveness and safety and shorter treatment course. Note that these agents are rarely initiated in the ED, as they require prolonged treatment courses and long-term monitoring by a PCP due to potential fluctuations in AST/ALT.

Tinea corporis, Tinea cruris, and Tinea pedis are generally responsive to topical creams such as terbinafine and butenafine, but oral antifungal agents may be indicated for extensive disease, failed topical treatment or immunocompromised patients. Tinea cruris (C), also known as jock itch, most commonly affects adolescent and young adult males, and involves the portion of the upper thigh. The scrotum itself is usually spared in Tinea cruris, but involved in candidiasis. Tinea corporis (B), also known as ringworm, typically presents as a red, annular, scaly, pruritic patch with central clearing and an active border. Lesions may be single or multiple and the size generally ranges from 1 to 5 cm, but larger lesions and confluence of lesions can also occur. Tinea corporis may be mistaken for many other skin disorders, especially eczema, psoriasis, and seborrheic dermatitis. A potassium hydroxide (KOH) preparation is often helpful when the diagnosis is uncertain based on history and visual inspection. Tinea pedis (D), athletes foot, typically involves the skin between the toes, but can spread to the sole, sides, and dorsum of the involved foot .The acute form presents with erythema and maceration between the toes, sometimes accompanied by painful vesicles.

This child presents with a mild case of impetigo and can be treated with topical mupirocin. The rash is characterized by a slowly progressing pustular eruption and is commonly seen in preschool age children. The most common causative agent is Staphylococcus aureus with group A streptococcus as a less common etiology. It most commonly presents on the face and other exposed areas and typically begins with a single pustule that develops into multiple lesions over time. The original erythematous vesicle will break leaving red erosions covered in a golden yellow crust. The lesions should not be painful but may be pruritic. The lesions are contagious. First line treatment for limited extent of lesions is with topical antibiotics including mupirocin 2% ointment. Mupirocin should not be used if methicillin-resistant strains are suspected.

This patient presents with signs and symptoms of cellulitis requiring antibiotic treatment covering the most likely pathogens. Cellulitis is a soft tissue infection involving the skin and subcutaneous tissue. It is characterized by erythema, swelling, local warmth and tenderness. Cellulitis can occur anywhere on the body but usually presents on the lower extremities, upper extremities and face. Staphylococcus aureus and Streptococcus pyogenes are the most commonly isolated organisms and antibiotics should be directed against these pathogens. The diagnosis is made clinically and there is no specific test that aides in diagnosis. Standard treatment is with immobilization, elevation, warm compresses and antibiotics. In the last 10-15 years, community acquired methicillin resistant S. aureus (CA-MRSA) has become a common causative organism. Cephalexin is a first generation cephalosporin with activity against manystreptococcus and staphylococcus species but not against MRSA. TMP-SMX is added to cephalexin when the cellulitis is associated with purulence. TMP-SMX is active against most strains of MRSA but does not have adequate activity against S. pyogenes. Per IDSA guidelines, for outpatients with purulent cellulitis (e.g., cellulitis associated with purulent drainage or exudate in the absence of a drainable abscess), empirical therapy (e.g. TMP-SMX) for CA-MRSA is recommended pending culture results. Empirical therapy for infection due to β-hemolytic streptococci is likely to be unnecessary.

Necrotizing fasciitis is an infection of the subcutaneous tissue that spreads rapidly across the fascial planes and is often fatal even with aggressive treatment. Risk factors for necrotizing infections include diabetes, vascular insufficiency, and immunosuppression. Classically patients have pain out of proportion to examination. Later findings include diffuse swelling, erythema, induration, and crepitus. The gold standard for diagnosis is direct visualization in the operating room by a surgeon. Surgeons may elect to perform a bedside biopsy prior to full exploration. Management includes aggressive IV hydration, broad-spectrum antibiotics, and surgical debridement.

The correct answer is strep pyogenes (group A strep). This patient’s presentation, particularly the sharply raised border, is classic for erysipelas which is typically caused by group A strep. The rash itself is caused by a streptococcal exotoxin. Treatment involves parenteral or oral antibiotics depending on the extent of the infection.
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