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Part V
Dermatologic
311© Springer International Publishing AG 2018
E. Sydney et al. (eds.), Handbook of Outpatient Medicine,
https://doi.org/10.1007/978-3-319-68379-9_19
Introduction
Rashes are common problems encountered in primary care
offices, dermatology practices, and emergency rooms that
often represent a diagnostic conundrum, even to the most
experienced practitioner. Many conditions produce rashes
that appear very similar clinically, and the differences distin-
guishing them are often subtle. It is important that the correct
diagnosis be made initially. Many conditions can be exacer-
bated by incorrect treatments, and lack of prompt interven-
tion can lead to significant morbidity in some cases and,
rarely, mortality. When approaching rashes, it is helpful to
generate a good differential diagnosis by categorizing the
rash based on its reaction pattern. Presented here is an algo-
rithmic approach to rashes that begins with five previously
described reaction patterns: papulosquamous, eczematous,
vascular, dermal, and vesiculobullous [1]. Each reaction pat-
tern is then subcategorized based on nuances in the appear-
ance, texture, and symptoms of various skin conditions.
Chapter 19
Rash
Alyssa Miceli and Karthik Krishnamurthy
A. Miceli, DO • K. Krishnamurthy, DO, FAOCD, FAAD (*)
Department of Dermatology, Orange Park Medical Center,
906 Park Avenue, Orange Park, FL 32073, USA
e-mail: Alyssa.miceli@gmail.com; kkderm@gmail.com
312
Decision-Making/Differential Diagnosis
The initial step in approaching a rash is to create a detailed
description of the rash. A good description includes shape,
color, primary lesions, secondary changes, distribution, and
configuration (see H & P). Next, categorize the reaction pat-
tern based on your description:
• Papulosquamous rashes are red scaly rashes.
• Eczematous rashes are red and itchy and can have scale,
crust, and lichenification (accentuation and thickening of
skin markings).
• Dermal rashes are rashes with no surface (or epidermal)
change.
• Vascular rashes are red and may be blanching or
non-blanching.
• Vesiculobullous rashes are rashes with blisters of varying
sizes.
In general, consider common conditions first while at the
same time ruling out life-threatening conditions promptly (i.e.,
severe drug reactions such as Stevens-Johnson syndrome (SJS),
toxic epidermal necrolysis (TEN), drug reaction with eosino-
philia and systemic symptoms, urticaria with angioedema,
staphylococcal scalded skin syndrome (SSSS), toxic shock syn-
drome (TSS) , erythroderma, meningococcemia, etc.) [2].
Papulosquamous
Generally speaking, this reaction pattern includes rashes with
red, scaly papules and plaques.
Psoriasiform
Psoriasis. Well-demarcated, red plaques with thick overlying
scale. Common locations include extensor surfaces (knees,
elbows), scalp, palms, and soles. Nail findings can aid in the
diagnosis and include pitting, oil spots, and onycholysis
(Fig. 19.1).
A. Miceli and K. Krishnamurthy
313
Seborrheic dermatitis. Erythema with overlying greasy scale
in a “seborrheic distribution” (oil- and hair-bearing areas).
Associated with HIV, Parkinson’s disease, and other neuro-
logic conditions [3].
Pityriasis rubra pilaris. Reddish-orange scaly plaques, kera-
totic follicular papules, palmoplantar keratoderma. Distinct
areas of uninvolved skin referred to as “islands of sparing”
are characteristic.
Tinea corporis. Annular or ring-shaped red, scaly plaques.
Raised border has more scale than the clearer center of the
lesion [3].
Pityriasiform
Pityriasis rosea. Oval-shaped pink to red scaly thin plaques in
“Christmas tree” distribution along the body folds. Herald
patch appears a few days before the other smaller lesions.
Located mostly on the trunk, it can involve extremities. This
can occur on the face in African Americans.
Secondary syphilis. Small red to brown scaly papules with
involvement of the palms and soles.
Fig. 19.1 Plaque psoriasis. Thick, red plaques with sharply demar-
cated borders and overlying silvery scale
19. Rash
314
Tinea versicolor. Tan to red or hypopigmented thin plaques
with fine scale. These are typically located on the upper chest,
upper back, and neck.
Lichenoid
Lichen planus (LP) five Ps. Purple, polygonal, planar, and pru-
ritic plaques. “Wickham striae” may be present. Lower extrem-
ities are a common location, but some people have mucosal
and penile lesions. Drug-induced LP is associated with NSAIDs,
diuretics, ACE inhibitors, and beta-blockers [3] (Fig. 19.2).
Erythroderma
Generalized erythema and scaling that affects >90% of the
body surface area. The underlying causes include preexisting
dermatoses (atopic dermatitis, psoriasis, seborrheic dermatitis),
cutaneous T-cell lymphoma, or drug reactions [3] (Fig. 19.3).
Eczematous
1. Acute eczema. Weeping, vesicular erythematous papules
and plaques that are very itchy. Geometric or linear con-
figuration indicates “outside job” and is a clue to diagnosis
[1]. Includes acute allergic/irritant contact dermatitis and
dyshidrotic eczema.
2. Subacute eczema. Eczematous lesions that progress, form-
ing scaly crust.
3. Chronic eczema. Characterized by lichenification, hyper-
pigmentation, and thicker scaly plaques.
Atopic dermatitis. Common in children, but can also be
seen in adults. Located in flexural areas. It is associated
with asthma, allergies, and an “itch-scratch” cycle. A diag-
nostic clue is that the middle part of the back (where
patient cannot reach to scratch) will be spared (Fig. 19.4).
A. Miceli and K. Krishnamurthy
Fig. 19.2 Lichen planus. Purple, polygonal, planar plaques on the
anterior lower extremity
Fig. 19.3 Erythroderma, Generalized erythema and exfoliative
scaling in a patient with underlying psoriasis
316
Fig. 19.4 Chronic eczema. Lichenification and hyperpigmented
papulonodules in the antecubital fossa of a child with atopic
dermatitis
Stasis dermatitis. Typically seen on the lower extremities in
elderly individuals. Underlying venous insufficiency, varicose
veins, and edema are present. Hyperpigmentation occurs from
hemosiderin deposition. Itching and overlying scale occurs.
Dermal
1. Subcutaneous
Panniculitis. Erythematous deep nodules:
(a) Septal: superficial thrombophlebitis, erythema nodo-
sum, or cutaneous polyarteritis nodosa
(b) Lobular: erythema induratum, Crohn’s disease, calci-
phylaxis, lupus panniculitis, or pancreatic panniculitis
(Fig. 19.5)
A. Miceli and K. Krishnamurthy
317
Fig. 19.5 Erythema nodosum. Tender, erythematous nodules over
the shins in a young female taking oral contraceptive pills
Cellulitis. Erythema, edema, warmth and pain with/
without fever, and lymphadenopathy
2. Inflammatory
Lupus erythematosus. Malar erythema (spares nasolabial
fold) with confluent erythema and edema or maculopapular
lesions in sun-exposed areas. Oral ulcers may be present.
Granuloma annulare. Groups of 1–2 mm papules in an annu-
lar arrangement often found on distal extremities, hands, feet,
fingers, and extensor aspects of the arms and legs.
Sarcoidosis. Purple-red or brown indurated circular
plaques. Erythema nodosum may be present.
3. Infectious
Erysipelas. Well-demarcated fiery-red indurated, tense,
often shiny, plaque that is most often on the lower extremi-
ties or face. Abrupt demarcation from healthy skin is a
classic clinical sign.
Deep fungal infections. Often rapidly spreading patch,
plaque, nodule, or abscess often with necrotic center, ulcers,
or sinuses. Causes include histoplasmosis, blastomycoses,
coccidioidomycoses, and cryptococcus.
Atypical mycobacterium, sporotrichosis, and cat-scratch disease.
Linear subcutaneous nodules with unilateral lymphadenitis.
19. Rash
318
4. Proliferative
This category includes various benign and malignant dermal
neoplasms or proliferations. The list of dermal proliferations is
long and includes various cysts, adnexal tumors (eccrine gland,
apocrine gland, hair tumors), tumors derived from collagen/
elastin, muscle cells, nerve cells, blood vessels, and melanocytic
lesions. Finally, what is referred to as the “purple plum” differ-
ential is considered, which includes amelanotic melanomas,
cutaneous metastases, sarcomas, vascular tumors (Kaposi sar-
coma and angiosarcoma), lymphomas, and leukemia cutis.
5. Depositional
A group of unrelated disorders characterized by deposi-
tion of substances within the dermis. This is broken down
into the type of substance deposited: lipid (xanthomas),
mucin (myxedema, granuloma annulare, necrobiosis
lipoidica diabeticorum), amyloid (primary, secondary, mac-
ular, or nodular), calcium (calciphylaxis, dystrophic, meta-
bolic), or urate (gout).
Vascular
Vascular rashes are red in color and are distinguished first by
whether or not they are blanching due to vasodilation.
Purpuric rashes are non-blanching due to red blood cell
extravasation. Palpable purpura indicates vasculitis.
1. Urticaria. Classic hive or wheal appearance: edematous, blanch-
ing erythematous plaques due to a type I hypersensitivity.
2. Toxic erythema. Diffuse and confluent blanching erythema-
tous macules and papules. These can be deadly. Etiologies
include viral exanthems, drug eruptions, and the following:
(a) Scarlet fever. Features multiple 1- to 2-mm punctate
papules with sandpapery feel. Treat with penicillin or
erythromycin.
(b) SSSS. Diffuse yellow-red tender erythema that pro-
gresses to large, flaccid bullae with desquamation. Treat
with penicillins, cephalexin, cefazolin, or TMP-SMX.
A. Miceli and K. Krishnamurthy
319
(c) TSS. Fever >102 °F, rash, late desquamation, straw-
berry tongue, pharyngeal redness, conjunctivitis. Treat
with clindamycin, vancomycin, or nafcillin.
(d) Kawasaki disease. Polymorphous rash, strawberry tongue,
conjunctivitis, redness and scaling of palms and soles, cer-
vical adenopathy. Treat with aspirin and IVIG [4].
(e) Stevens-Johnson syndrome/toxic epidermal necrolysis
(SJS/TEN). Diffuse erythema, bullae that become necrotic
followed by diffuse desquamation of the skin. Commonly
implicated drugs include NSAIDs, penicillins, sulfa drugs,
anticonvulsants, barbiturates, and allopurinol.
3. Erythema multiforme. Targetoid red papules with dusky
center that can be bullous. Involves palms and soles, unlike
many other rashes.
4. Vasculitis. Palpable purpura. Can be vesicular or bullous
[5] (Fig. 19.6).
(a) Hypersensitivity. Symmetric. Infection (HCV, group A
Streptococcus (GAS), autoimmune disease, drug,
malignancy, Henoch-Schonlein purpura.
(b) Septic: Asymmetric, often involving acral surfaces.
Meningococcemia, pseudomonas, gonococcemia, GAS.
Fig. 19.6 Palpable purpura on the lower extremity indicating leuko-
cytoclastic vasculitis
19. Rash