Generalized and Localized Rashes

Overview

Definition

A rash is an abnormal change in the skin’s color or texture.

Epidemiology

One of the most common conditions encountered by primary care physicians
In 2016, 1 in 4 people in the United States (84.5 million) were affected by skin disease.
1 in 3 people required a dermatology evaluation.
Maculopapular rashes are the most commonly seen generalized rash (95%).
Diagnostic errors in generalized rashes are common.

Etiology

The list of etiologies for rashes is long but can include irritants, allergens, infections, and inflammatory conditions.

Classification

Rashes are described and classified based on certain characteristics, which can assist with forming a differential diagnosis when evaluating a patient.

Configuration

The configuration refers to the shape or outline of lesions.

Circinate: round, circular
Arciform: forms a partial circle
Linear: appears straight
Serpiginous: meandering appearance
Annular: round or circular with central clearing
Target: a series of concentric rings
Gyrate: a series of connecting arcs
Zosteriform: appears to follow a dermatome

Rash configurations — Visualization of different rash configurations
Image by Lecturio.

Morphology

The morphology is based on the size and consistency of the lesions.

Flat lesions:
- Macule: nonpalpable lesion < 1 cm in diameter
- Patch: nonpalpable lesion > 1 cm in diameter
Raised lesions:
- Papule: elevated lesion < 1 cm in diameter
- Plaque: flat-topped elevated lesion > 1 cm in diameter
- Nodule: deep, solid or cystic, elevated lesion > 1 cm in diameter
- Wheal: irregularly shaped, edematous, raised, transient plaque
Blistering lesions:
- Vesicle: blister filled with clear fluid, < 1 cm diameter
- Bulla: blister filled with fluid, > 1 cm diameter
- Pustule: blister filled with pus
Disruption of the epidermis:
- Erosion: partial-thickness loss of the epidermis
- Fissure: a crack or split that extends into the dermis
- Ulcer: full-thickness loss of the epidermis that extends into the dermis

Rash morphology — Visualization of different rash morphologies
Image by Lecturio.

Rash morphology flowchart — Schematic to help differentiate different morphologies based on their size and characteristics
Image by Lecturio.

Small, flat macules due to rubella
Image: “Rubella” by CDC. License: Public Domain

Large patches of hypopigmentation in vitiligo — Small, flat macules due to rubella
Image: “Rubella” by CDC. License: Public Domain

Secondary characteristics

Crust: dried exudate on the skin
Scale: flakes or plates of desiccated epidermis
Lichenification: leathery thickening of the skin with exaggerated skin markings
Excoriation: linear skin erosions, often caused by scratching
Edema: swelling of the tissue
Scar: fibrous tissue development after an injury

Demonstration of an overlying crust — An overlying crust
Image: “Diabetic dermopathy (“shin spots”) and diabetic bullae (“bullosis diabeticorum”) at the same patient” by Brzezinski P, Chiriac AE, Pinteala T, Foia L, Chiriac A. License: CCC BY 3.0

Scale on a herald patch of pityriasis rosea — An overlying crust
Image: “Diabetic dermopathy (“shin spots”) and diabetic bullae (“bullosis diabeticorum”) at the same patient” by Brzezinski P, Chiriac AE, Pinteala T, Foia L, Chiriac A. License: CCC BY 3.0

Distribution

Localized: Lesions are confined to a specific area.
Generalized: Lesions are dispersed throughout the body.
Symmetric: similarly affects both sides of the body
Asymmetric: unilateral or affects both sides of the body differently
Discrete: separate, distinct lesions
Grouped: clusters of lesions
Confluent (coalescing): Smaller lesions merge together.
Cleavage plane: Lesions are arranged along the lines of skin tension.

Clinical Presentation and Diagnosis

The diagnosis for many conditions is purely clinical and based on the patient’s history and physical exam.

History

Onset (including the location of initial onset)
Time frame:
- Acute or chronic
- Relapsing-remitting
Progression
Aggravating and alleviating factors
Associated symptoms:
- Fever
- Pruritus
- Pain
- Malaise
- Cough
Other pertinent history:
- Allergies
- Recent travel
- Insect, plant, or animal exposure
- Occupational history
- New home products
- Drug exposure
- Sick contacts
- Chronic illnesses
- Sexual history

**Table: Summary of possible conditions based on patient’s history**
Patient’s history	Associated disease
Chronic illness	Dermatitis herpetiformis Seborrheic dermatitis
Contact with ill persons	5th disease Meningococcemia Rubella Roseola Rubeola Scarlet fever Varicella
Drug exposure	Lupus Drug eruption Urticaria Stevens-Johnson syndrome
Occupational or environmental exposure	Contact dermatitis
Insect and arthropod exposure	Insect bites Lyme disease Rickettsialpox Rocky Mountain spotted fever Scabies
Recent systemic symptoms	5th disease HIV acute exanthem Kawasaki disease Meningococcemia Roseola Rubella Rubeola Scarlet fever Varicella
Sexual history	HIV acute exanthem Secondary syphilis Disseminated gonorrhea
Travel	Insect bites Lyme disease Rickettsialpox Rocky Mountain spotted fever

HIV: human immunodeficiency virus

Physical exam

A full skin exam should be performed.

Appearance:
- Number of lesions
- Configuration and borders
- Morphology
- Color
- Presence of scale or crusts
Distribution:
- Diffuse or localized
- Symmetrical or asymmetrical
- Dermatomal
- Clustered or grouped
- Mucosal involvement
- Atypical sites (e.g., palms and soles)
Palpation of lesions:
- Raised
- Flat
- Texture changes
- Induration
- Blanching with pressure
In patients with bullae, check for Nikolsky sign:
- Extension of skin blistering or sloughing by applying pressure
- Demonstrates skin detachment
In patients with plaques, check for Auspitz sign: pinpoint bleeding after scraping plaques
Other physical exam findings to evaluate for:
- Vital signs
- Lymphadenopathy
- Conjunctivitis
- Pharyngitis
- Heart murmur
- Hepatosplenomegaly
- Joint swelling
- Neurologic deficits

Testing

A diagnostic workup may be performed if the history and physical exam do not provide enough clues to the diagnosis. The differential diagnosis will dictate which studies should be performed.

Biopsy with microscopic examination:
- There are no widely accepted guidelines with indications for skin biopsy.
- Immunofluorescence can be helpful.
Laboratory tests are indicated if there are systemic symptoms.
- CBC → evaluate for eosinophilia, neutrophilia, or thrombocytopenia
- Basic metabolic panel and liver function panel → evaluate for systemic renal and hepatic involvement
- ANAs → a good initial test if an autoimmune etiology is being considered
- Serologic testing for various infectious causes
Allergy testing:
- Patch testing
- Skin prick testing
- Serum IgE studies

Management

The management of a rash depends on the underlying condition. Many rashes will be self-limited and may not require any treatment.

Basic management:
- Identify and avoid aggravating factors.
- Supportive therapies:
  - Low-heat baths
  - Mild soaps
  - Emollients
  - Skin moisturizers
Symptom management for pain and pruritis:
- Acetaminophen
- NSAIDs
- Antihistamines
For inflammatory conditions:
- Infection should be ruled out.
- Topical steroids:
  - Hydrocortisone
  - Triamcinolone
  - Clobetasol
  - Betamethasone
- Systemic steroids
For infectious causes:
- Antibiotics
- Antifungals
- Antivirals
Appropriate management for underlying systemic conditions

Comparison of Generalized Rashes

Noninfectious conditions

**Table: Summary of common noninfectious generalized rashes**
Condition	Features	Diagnosis	Management
Atopic dermatitis (eczema)	Type IV hypersensitivity reaction Ranges from erythema to lichenification to erythroderma Scaly patches or plaques Pruritus Distribution is typically over flexor surfaces.	Clinical diagnosis Serum IgE levels Skin prick tests Patch tests	Avoid triggers. Symptomatic therapy Emollients Topical corticosteroids Topical calcineurin inhibitors Phototherapy Immunosuppressants
Drug eruption	Often an immune-mediated hypersensitivity reaction Ranges in severity from urticaria and maculopapular eruptions to EM, SJS, and TEN Lesions may include: Edematous wheals Diffuse maculopapular lesions Target lesions Cutaneous bullae Sloughing of skin and mucosa Systemic symptoms	Clinical diagnosis Skin biopsy is rarely needed.	Withdrawal of the offending drug Symptomatic therapy Supportive care
Pityriasis rosea	Idiopathic Single round, ovoid, salmon-colored patch (“herald patch”) Followed by a widespread exanthem with scale “Christmas tree” distribution on back Pruritus	Clinical diagnosis	No intervention is needed. Symptomatic management
Lichen planus	Idiopathic Cell-mediated inflammatory disease Flat-topped, papular, purple lesions Pruritus Includes genitalia, nails, scalp, and mucous membranes	Clinical diagnosis Biopsy for confirmation	Topical steroids
Psoriasis	Cell-mediated inflammatory disease Well-circumscribed, salmon-colored plaques Silvery scales Seen on the scalp and extensor surfaces	Clinical diagnosis Biopsy is rarely needed.	Local therapy: Topical steroids Calcitriol Topical retinoids Phototherapy Systemic therapy: Methotrexate Cyclosporine Apremilast Biologic agents

Note: Although pityriasis rosea and lichen planus are considered idiopathic, they have been associated with certain viruses.
EM: erythema multiforme
SJS: Stevens-Johnson syndrome
TEN: toxic epidermal necrolysis

Erythema and lichenification in the kneefolds of a patient with atopic dermatitis
Image: “Role of the skin microbiome in atopic dermatitis” by Salava A, Lauerma A. License: CC BY 4.0

Edematous wheals suggestive of urticaria. This can be a manifestation of a drug eruption. — Erythema and lichenification in the kneefolds of a patient with atopic dermatitis
Image: “Role of the skin microbiome in atopic dermatitis” by Salava A, Lauerma A. License: CC BY 4.0

Infectious conditions

**Table: Summary of common infectious generalized rashes**
Condition	Features	Diagnosis	Management
Hand-foot-and-mouth disease	Caused by coxsackievirus type A Painful oval-shaped vesicles on hands, feet, buttocks, and oral mucosa Associated with fever	Clinical diagnosis	Symptomatic treatment
Roseola infantum (exanthem subitum)	Caused by HHV-6 or -7 Rose-pink maculopapular rash Mostly on the chest and abdomen but the back, face, and extremities can be involved Preceded by high fever and cervical lymphadenopathy	Clinical diagnosis	Symptomatic treatment
Measles (rubeola)	Caused by the measles virus Maculopapular rash that begins on the face and spreads to the trunk and extremities Koplik spots on the buccal membrane Associated with a high fever, cough, coryza, and conjunctivitis	Clinical diagnosis	Symptomatic treatment
Rubella (German measles)	Caused by rubella virus Fine, pink macules on the face and neck Becomes pinpoint and spreads to the trunk and extremities Less extensive than measles Forschheimer spots (petechiae on the soft palate) Associated with fever, lymphadenopathy, and conjunctivitis	Clinical diagnosis Serologic testing	Symptomatic treatment
5th disease (erythema infectiosum)	Caused by parvovirus B19 Initial prodromal symptoms “Slapped cheek” rash Followed by a morbilliform rash on the torso and extremities	Clinical diagnosis IgM or PCR testing is rarely needed.	Symptomatic treatment
Scarlet fever	Caused by Streptococcus pyogenes Begins with fever and sore throat Flushed cheeks Strawberry tongue Sandpaper-like rash on neck, trunk, and extremities Pastia’s lines	Clinical diagnosis Rapid antigen or throat culture to confirm	Penicillin Amoxicillin
Chickenpox	Caused by varicella-zoster virus Rash appears in crops and progresses from macules to papules to vesicles on a red base Lesions eventually crust. Intense pruritis Begins on trunk and spreads to the face and extremities Prodrome of fever and malaise	Clinical diagnosis Serologic testing may be done to confirm the diagnosis.	Symptomatic treatment Consider antiviral therapy (acyclovir).

HHV: human herpesvirus
PCR: polymerase chain reaction

Painful vesicles on a hand (A) and foot (B) due to hand-foot-and-mouth disease
Image: “Hand, foot and mouth disease: changing Indian scenario” by Rao PK, Veena K, Jagadishchandra H, Bhat SS, Shetty SR. License: CC BY 3.0, edited by Lecturio.

Diffuse maculopapular rash on the chest and abdomen due to roseola infantum — Painful vesicles on a hand (A) and foot (B) due to hand-foot-and-mouth disease
Image: “Hand, foot and mouth disease: changing Indian scenario” by Rao PK, Veena K, Jagadishchandra H, Bhat SS, Shetty SR. License: CC BY 3.0, edited by Lecturio.

Comparison of Common Localized Rashes

**Table: Summary of common localized rashes**
Condition	Features	Diagnosis	Management
Contact dermatitis	Type IV hypersensitivity reaction from allergens or irritants Maculopapular or vesicular rash Erythema and swelling Weeping, scaling, or crusting Pruritis or burning pain	Clinical diagnosis Patch testing	Avoid causative agents. Topical steroids Antihistamines Emollients
Tinea corporis	Caused by a dermatophyte infection Annular patches or plaques with raised, scaly borders Expand peripherally Central clearing Pruritis	KOH preparation Fungal culture	Topical or oral antifungals
Seborrheic dermatitis	Unknown etiology Erythematous, well-demarcated plaques Greasy yellow scales Found on the scalp, face, trunk, and intertriginous areas	Clinical diagnosis Biopsy to confirm	Topical antifungals Topical steroids Calcineurin inhibitors Keratolytic agents
Impetigo	Caused by Staphylococcus aureus and S. pyogenes Evolution of papules to vesicles to pustules Honey-colored crusts Bullous form: large, flaccid bullae	Clinical diagnosis Cultures are rarely needed.	Mild-to-moderate cases: topical antibiotics Bullous or severe cases: oral antibiotics
Cellulitis	Bacterial infection of the dermis and subcutaneous tissues Erythema and induration Warm to the touch Poorly demarcated	Clinical diagnosis Blood cultures if sepsis is present	Penicillins Vancomycin for MRSA
Erysipelas	A more superficial bacterial infection than cellulitis Involves the upper dermis and superficial lymphatics Well-defined erythema with raised demarcation Pain and tenderness	Clinical diagnosis Blood cultures if sepsis is present	Penicillins Vancomycin for MRSA
Necrotizing fasciitis	Life-threatening bacterial infection of the subcutaneous tissues and fascia Rapidly progressive erythema, swelling, and edema Severe pain Bullae and necrosis Systemic toxicity	Clinical diagnosis Blood and tissue culture Imaging studies	Surgical debridement Broad-spectrum IV antibiotics Hemodynamic support
Herpes zoster (shingles)	Caused by reactivation of the varicella-zoster virus Vesicular eruption in a dermatomal distribution Rash is preceded by pain. Complicated by postherpetic neuralgia	Clinical diagnosis PCR Tzanck smear	Prevented by vaccine Antiviral agents may reduce duration of symptoms. Symptomatic therapy

IV: intravenous
MRSA: methicillin-resistant S. aureus
ESR: erythrocyte sedimentation rate
KOH: potassium hydroxide

A pruritic, vesicular eruption due to contact dermatitis
Image: “Neoprene Orthopaedic Supports: An Underrecognised Cause of Allergic Contact Dermatitis” by Hawkey S, Ghaffar S. License: CC BY 3.0

Annular, scaling lesion of tinea corporis — A pruritic, vesicular eruption due to contact dermatitis
Image: “Neoprene Orthopaedic Supports: An Underrecognised Cause of Allergic Contact Dermatitis” by Hawkey S, Ghaffar S. License: CC BY 3.0

References

Ely JW, Osheroff JA, Ebell MH, et al. Analysis of questions asked by family doctors regarding patient care. BMJ. 1999;319(7206):358–361.
Fleischer AB Jr, Feldman SR, McConnell RC. The most common dermatologic problems identified by family physicians, 1990–1994. Fam Med. 1997;29(9):648–652.
Fleischer AB Jr, Feldman SR, Bullard CN. Patients can accurately identify when they have a dermatologic condition. J Am Acad Dermatol. 1999;41(5 pt 1):784–786.
Norman GR, Rosenthal D, Brooks LR, Allen SW, Muzzin LJ. The development of expertise in dermatology. Arch Dermatol. 1989;125(8):1063–1068.
Bircher, A. (2020). Exanthematous (maculopapular) drug eruption. UpToDate. Retrieved Feb 10, 2021, from https://www.uptodate.com/contents/exanthematous-maculopapular-drug-eruption
Armstrong, C.A. (2021). Approach to the clinical dermatologic diagnosis. In Corona, R. (Ed.), UpToDate. Retrieved February 26, 2021, from https://www.uptodate.com/contents/approach-to-the-clinical-dermatologic-diagnosis
Bickers DR, Lim HW, Margolis D, Weinstock MA, Goodman C, Faulkner E et al. (2006). The burden of skin diseases: 2004 a joint project of the American Academy of Dermatology Association and the Society for Investigative Dermatology. Journal of the American Academy of Dermatology 55:490-500.
Ely, J. and Stone, M. (2010). The Generalized Rash: Part I. Differential Diagnosis. American Family Physician. 81(6):726-734.
Ely, J. and Stone, M. (2010) The Generalized Rash: Part II. Diagnostic Approach. American Family Physician. 81(6):735-739.

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Table of Contents

Overview

Definition

Epidemiology

Etiology

Classification

Configuration

Morphology

Secondary characteristics

Distribution

Clinical Presentation and Diagnosis

History

Physical exam

Testing

Management

Comparison of Generalized Rashes

Noninfectious conditions

Infectious conditions

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Comparison of Common Localized Rashes

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References

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