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Image from Wikimedia Commons | Mariegriffiths.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Grouped herpetiform vesicles of herpes zoster (shingles) at day 6 are shown.

Skin rashes caused by bacterial, viral, or fungal etiologies are common presenting complaints to primary care clinics, emergency departments, and dermatologists. Although many presenting symptoms overlap, discrete, identifiable factors for each disease can aid in diagnosis and treatment. For example, herpes zoster is a cutaneous and neurologic disorder caused by reactivation of the varicella-zoster virus (VZV).[1] Immunodeficiency/immunosuppression, radiation, trauma, medications, stress, and other infections have been proposed as triggers.[1] Erythema, regional lymphadenopathy, and the above-mentioned grouped herpetiform vesicles develop, with the cutaneous findings typically being unilateral and usually not crossing the midline.[1]

Image from Medscape.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

In herpes zoster, the clusters of vesicles are initially clear (shown), but they may then become cloudy and may rupture, crust, and involute.[1] For some individuals, the pain does not resolve and may persist for years—a condition referred to as post-herpetic neuralgia (PHN).[1] Antiviral agents given early in the disease course may shorten the recovery period and decrease the chance of PHN.[2] A vaccine is available and is recommended by the Centers for Disease Control and Prevention (CDC) for individuals 50 years of age or older. This vaccine reduces the risk of developing shingles by 84.7-96.6%, and PHN by 88.8-91.2%.[3]

Image from the CDC | Dr. Herrmann.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Herpes simplex viruses (HSVs) are DNA viruses that cause acute skin infections, evident as grouped vesicles on an erythematous base. HSV-1 usually occurs around the mouth or face (shown), while HSV-2 typically develops on the genitals, buttocks, or perianal area.[4] Infection results from transmission of body fluids onto a mucous membrane or open skin from an actively shedding individual to a susceptible person.[5] Although there is no cure, most infections are self-limited, and antiviral therapy (eg, acyclovir, famciclovir, valacyclovir) will shorten the course of symptoms and may help to prevent dissemination and transmission.[6]

Can you correctly diagnose the following rashes?

Image from Wikimedia Commons | Camiloaranzales.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

A 9-year-old boy presented with a skin rash (shown) that was accompanied by a low-grade fever and intense pruritus. What is the name of the infectious agent and its resultant rash? How is this microscopic organism transmitted?

Image from Wikimedia Commons | F malan.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Answer: Chickenpox, caused by varicella-zoster virus (VZV), which is highly contagious and is acquired via inhalation of airborne respiratory droplets or direct vesicle contact[7,8]

The characteristic clear vesicle of chickenpox, surrounded by an erythematous halo, is shown.

Chickenpox occurs mostly in children younger than 10 years, generally appearing 10-21 days after contact with an infected person.[8] It presents first on the face, torso, or scalp, followed by the rest of the body.[7,8] The virus invades the capillary endothelial cells and epidermis, producing intercellular and intracellular edema and causing formation of the above-mentioned vesicles. Lesions will subsequently develop central umbilication and crusting. On examination, vesicles in all stages of development are typically present.

The disease usually resolves spontaneously over 5-10 days. Treatment is generally supportive.[8] However, adults may have significant morbidity from systemic involvement and are often given antiviral medications as early as possible. One should avoid the use of aspirin (associated with Reye syndrome) and ibuprofen (associated with severe secondary infections), in children.[8]

Image courtesy of Justin Finch, MD.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

This patient presented with lesions that appeared as firm, smooth, umbilicated papules about 2-6 mm in diameter. What is the cause of this skin manifestation?

Image from Medscape.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Answer: Molluscum contagiosum

Molluscum contagiosum is a cutaneous infection that is caused by a large DNA poxvirus and manifests as raised, pearl-like papules/nodules (shown) with a central depression and a plug of cheesy material.[9-11] Affected areas include the face, neck, armpits, arms, and hands (from direct skin contact or sharing of contaminated towels, sports equipment, or toys), as well as the genitals (from sexual contact).

The papules may be painless or pruritic and tender and exist either in clusters or as widely distributed lesions; they also vary in color (flesh color, white, translucent, or yellow) and range in number from one to several hundred.[9,10] Immunocompromised patients have larger, more numerous, refractory lesions.[10] This condition is typically self-limited, but to prevent autoinoculation, surgical removal (eg, through curettage, cryotherapy, or laser therapy) or pharmacotherapy may be appropriate for lesions that do not resolve after several months.[9,10,12]

Image from Wikimedia Commons | KlatschmohnAcker.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

This patient presented with cutaneous lesions on the hands, feet, and buttocks. These 2- to 10-mm erythematous macules may develop into a central, gray, oval vesicle. The lesions are elliptical, with the long axis parallel to the skin lines. What is the cause of these skin lesions?

Image from Wikimedia Commons | Ngufra.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Answer: Hand-foot-and-mouth disease

Hand-foot-and-mouth disease (HFMD) is a viral illness with oral and distal-extremity lesions. The oral lesions are normally 2- to 3-mm vesicles on an erythematous base. HFMD is most commonly caused by coxsackievirus A16 and typically affects children and infants.[13,14] The disease is highly contagious during the first week of infection and may lead to epidemics from direct contact with nasal and oral secretions or fecal material. The incubation period typically averages 3-7 days. Symptoms include fever, rash, headache, sore throat, oropharyngeal ulcers, and loss of appetite.[13] Care is typically supportive, with antipyretics and anesthetics used for symptomatic relief on a case-by-case basis.

Image from Medscape.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

This patient presented with an illness that has three distinct phases with a mild prodrome. In the first phase (2-4 days), bright-red erythema appears over the cheeks in a classic slapped-cheek appearance (shown) that spares the nasal, periorbital, and perioral regions. In the second phase (1-4 days), an erythematous macular-to-morbilliform eruption occurs, predominantly on the extensor surfaces of the extremities. In the final stage (several days to weeks), the eruption fades, leaving behind a reticulated, lacy pattern. What is the cause of this viral illness?

Image courtesy of Justin Finch, MD.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Answer: Erythema infectiosum

Erythema infectiosum, or fifth disease, is a common childhood exanthem caused by human parvovirus B19.[15,16] Transmission occurs via aerosolized respiratory droplets or through blood or blood products (eg, maternal-fetal transmission).[15,16] The condition has an incubation period of 4-14 days (up to 20 days).[16] Symptoms include fever, headache, and runny nose, followed by a pruritic rash on the face ("slapped cheek"), as well as on the torso and extremities.[15,16] The disease is typically self-limited (7-10 days) and resolves without complications or sequelae in children. The virus may also result in acute or persistent arthropathy, as well as so-called gloves-and-socks syndrome, characterized by papular, purpuric eruptions on the hands and feet. In addition, an acute cessation of red blood cell production may be triggered by the virus, with transient aplastic crisis, chronic red cell aplasia, or hydrops fetalis resulting. Also, if erythema infectiosum affects a pregnant woman, it can cause congenital anemia in the fetus/newborn.

Patients with human immunodeficiency virus (HIV) or blood disorders such as iron-deficient anemia, sickle cell disease, or thalassemia are at increased risk.[17] Treatment is generally supportive on a case-by-case basis.[15,16] Patients who develop arthralgia may be treated with oral analgesics; those who suffer from pruritus may use antihistamines or topical antipruritic lotions.

Image from Wikimedia Commons | James Heilman, MD.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

This patient presented with complaints of a solitary, salmon-colored macule that enlarged over several days to become a patch with fine scales and a well-demarcated border. Over the next several weeks, a generalized exanthem developed with bilateral, symmetrical macules 0.5-1.5 cm in diameter; it was oriented along cleavage lines and was characterized by mild to moderate pruritus. What is the cause of this pruritic dermatologic manifestation?

Image from Wikimedia Commons | James Heilman, MD.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Answer: Pityriasis rosea

Pityriasis rosea is a benign papulosquamous disease that occurs most often in the spring and fall, like many viral exanthems.[18] It begins as a solitary macule that is 2-10 cm in diameter, termed a "herald" or "mother" patch; after several days, more lesions ("daughter" patches) appear on the torso and extremities.[18,19] The generalized exanthem typically lasts for 6 weeks (range, 4-8 weeks; occasionally >8 weeks).[18,19] The exact etiologic agent is not known, but immunologic data suggest a viral etiology. Treatment is largely symptomatic for relief of pruritus, with topical steroids and oral antihistamines used.[18,19]

Image courtesy of Justin Finch, MD.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

The above skin infection is generally limited to the epidermis and expands in a centrifugal pattern. Transmission is via direct skin-to-skin contact. Patients may be asymptomatic or complain of a pruritic or burning sensation. The lesion appears as an erythematous, scaly plaque that may enlarge rapidly (shown). Scales, crust, papules, vesicles, or bullae may develop along the advancing border.

What is the cause of this skin manifestation?

Image from Wikimedia Commons | James Heilman, MD.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Answer: Tinea corporis

Tinea is a superficial dermatophyte infection characterized by scaly, inflammatory or non-inflammatory patches. Its classification is based on the affected region, such as tinea pedis, for feet ("athlete's foot"); tinea corporis, for body; tinea capitis, for head/scalp; and tinea cruris, for groin ("jock itch").[20,21] Tinea may be caused by one of three dermatophytes: Trichophyton (most common),[21,22] Microsporum,[21,22] and Epidermophyton.[22] The dermatophytes preferentially inhabit warm, moist areas of the skin and may spread by skin contact or by contact with contaminated items or infected animals.[20,21] The diagnosis may be made with a potassium hydroxide (KOH) preparation from a skin scraping.

Image from Medscape.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

The boy in the above image has tinea capitis caused by an infection with the fungus Microsporum canis.

Tinea capitis, or ringworm of the scalp, is considered to be a form of superficial mycosis or dermatophytosis;[23.24] it is the most common pediatric dermatophyte infection worldwide.[23] The infection is generally spread by direct contact with the lesion, sharing of personal items (eg, combs/brushes, hats), and contact with infected pets (eg, cats, dogs).[24] The diagnosis is confirmed by examination and culture of hair and skin scrapings. Oral antifungals (eg, griseofulvin, terbinafine, itraconazole) are used to treat the condition over 4-8 weeks.[24]

Image from Wikimedia Commons | RafaelLopez.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Cellulitis (shown) is a non-necrotizing bacterial infection of the dermis and hypodermis.[25,26] The most common organisms involved are Streptococcus pyogenes and Staphylococcus aureus. Small breaks in the skin allow organisms to gain entrance to the dermis and multiply.[25,26] In rare cases, particularly in immunocompromised patients, hematogenous or metastatic seeding may occur.[26] Patients commonly report fevers, chills, pain, swelling, tenderness, erythema, and warmth.[25,26] The borders of cellulitis are typically not elevated or sharply demarcated.[26] In general, uncomplicated cases may not require laboratory studies;[26] for more severe infections, obtain blood cultures (or fluid cultures from lesions), complete blood counts, and other tests as needed.[25,26]

Image from Wikimedia Commons | Åsa Thörn.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Skin lesions of impetigo are shown above.

Impetigo is a gram-positive bacterial infection of the superficial layers of the epidermis; the most common causative organisms are S aureus and group A beta-hemolytic streptococci.[27] Methicillin-resistant S aureus (MRSA) is also becoming a common cause. Impetigo may be classified as bullous or non-bullous. Infection typically occurs via skin breakage from skin diseases or from excoriation or other trauma. Patients are either colonized in the anterior nares or infected via organisms passing from one individual to another through direct contact with the lesions. Symptoms and signs include pruritic blisters, lymphadenopathy, and skin sores.[27] The diagnosis is usually clinical.

Treatment for impetigo typically involves topical antibiotics (eg, mupirocin, retapamulin) and local wound care.[27] If MRSA is suspected, antimicrobial therapy relies on susceptibility testing.

Image courtesy of Brett Sloan, MD.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

The dermatologic manifestation shown appears as multiple, small papules; typically, it presents as pustules on an erythematous base, pierced by a central hair. Two days ago, this patient used a hot tub. What is the name of this condition? What is the most common organism associated with it?

Image from Wikimedia Commons | James Heilman, MD.

12 Rashes You Need to Know: Common Dermatologic Diagnoses

Lars Grimm, MD, MHS | February 10, 2021 | Contributor Information

Answers: Folliculitis; S aureus

Folliculitis is inflammation within the wall and ostia of one or more hair follicles, creating a pustule.[28,29] Different causes have been identified, including infection, trauma, friction, perspiration, and occlusion. The most common infectious organism is S aureus,[28,29] although gram-negative organisms have been found in patients on long-term antibiotic therapy, and Pseudomonas may be found in patients who use hot tubs or wet suits.[29]

Symptoms and signs may include pruritic rash and pustules in hair-bearing sites, most commonly the face, scalp, neck, groin, and genital area. The diagnosis of folliculitis is generally clinical, and the condition is typically self-limited.[29]

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Nonmelanoma Skin Cancers You Need to Know

Nonmelanoma skin cancer is the most common form of human neoplasia, with millions of cases diagnosed annually. Do you know which of these cases are most likely to metastasize?Medscape Reference Slideshow, Jan 2021
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Herpes Zoster

The varicella-zoster virus (VZV) (see the image below) is the etiologic agent of the clinical syndrome of chickenpox (varicella). Zoster, a different clinical entity, is caused by reactivation of VZV after primary infection.Medscape Drugs & Diseases, Aug 2020
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Tinea Cruris

Tinea cruris, a pruritic superficial fungal infection of the groin and adjacent skin, is the second most common clinical presentation for dermatophytosis.Medscape Drugs & Diseases, Sep 2020
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