Figurate Erythemas

Question 1

Which figurate erythema is strongly associated with internal malignancy and what is its characteristic skin appearance?

Answer 1

Question 2

Dx and DDX?

Answer 2

Erythema Gyratum Reapens

EAC

Question 3

What is the typical rate of expansion of lesions in EGR, and how long before or after cancer diagnosis can they appear?

Answer 3

Expansion rate: ~1 cm/day

Timing: Lesions may appear up to 1 year before or after the diagnosis of malignancy

Most commonly: 4 to 9 months prior to cancer diagnosis (in 80% of cases)

Question 4

Which figurate erythema is associated with rheumatic fever, and what other major clinical features are part of the Jones criteria?

Answer 4

Erythema Marginatum

The Jones major criteria for rheumatic fever (remember: JONES) include:

Joint involvement – migratory polyarthritis

**O **– (Heart shape) Carditis

Nodules – Subcutaneous, painless, bony prominences

Erythema marginatum

Sydenham’s chorea

And minor criteria include:

Fever, arthralgia, ↑ ESR/CRP, prolonged PR interval on ECG

Question 5

Describe the cutaneous features and common locations of erythema marginatum.

Answer 5

Erythematous macules or annular/polycyclic plaques
* Faint, non-indurated borders
* Sometimes with central clearing
* Not scaly

Distribution:
* Trunk, axillae, and proximal extremities
* Spares face, palms, and soles

Features:
* Migratory, often expanding 2–12 mm in half a day
* Asymptomatic
* Seen during the active phase of rheumatic fever, especially when carditis is present

Question 6

Which figurate erythema begins as a pink papule and expands centrifugally with trailing white scale? What’s a classic infectious trigger?

Answer 6

Erythema Annulare Centrifugum (EAC)
* starts as a firm pink papule and expands centrifugally, forming:
* Annular or polycyclic lesions
* With central clearing and a trailing white scale

A classic infectious trigger is tinea (dermatophyte infection)

Other triggers include poxvirus, EBV, HIV, and pseudomonas

Question 7

Histological features of EAC?

Answer 7

✅ Superficial EAC shows:

Mild spongiosis

Focal parakeratosis

A tight, dense perivascular lymphohistiocytic infiltrate — classically described as a “coat-sleeve” pattern

✅ Deep EAC:

Has a deeper perivascular infiltrate in the mid-to-deep dermis

Still composed of lymphohistiocytic cells, but with minimal scale

Question 8

Which figurate erythema is the first sign in 90% of Lyme disease cases, and what size does the lesion typically exceed?

Answer 8

Erythema migrans

the first sign in ~90% of Lyme disease cases.

Appears 7–15 days after Ixodes tick detachment

Lesion typically exceeds 5 cm in diameter

Expands centrifugally from the bite site

May be accompanied by flu-like symptoms in early localized disease

Question 9

Name two systemic complications seen in early disseminated Lyme disease.

Answer 9

Two hallmark complications of early disseminated Lyme disease:

**Cardiac conduction defects **— especially atrioventricular (AV) block

Neurologic involvement — such as:
* Cranial neuropathies (commonly Bell’s palsy)
* Radiculopathies
* Meningitis

Also may see:
* Migratory arthralgias
* Iritis

Question 10

What is the first-line medication for treating erythema migrans in adults?

Answer 10

Doxycyline 100mg BS for 10 - 21 days

Question 11

What are the triggers for EAC?

Answer 11

Key triggers include:

Infections: Tinea, EBV, HIV, etc.

Drugs: NSAIDs, diuretics, antimalarials, amitriptyline, rituximab, etc.

Foods: Blue cheese (due to Penicillium species)

Others: Pregnancy, underlying malignancy

Question 11

Erythema marginatum is often missed due to its subtlety. Name two distinguishing features that differentiate it from urticaria, despite their superficial resemblance.

Answer 11

Duration of lesions:
* Erythema marginatum: Lesions are transient but persist longer than 24 hours, and often migrate slowly over hours
* Urticaria: Lesions typically resolve within 24 hours

Symptoms:
* Erythema marginatum: Asymptomatic, non-pruritic
* Urticaria: Pruritic and often edematous

Morphology:
* Erythema marginatum: Annular, polycyclic patches with faint, non-indurated edges and central clearing
* Urticaria: Raised, edematous wheals, often uniform in color, with no central clearing

Context:
Erythema marginatum occurs during the active phase of rheumatic fever, often with carditis

Question 12

A 47-year-old man presents with several annular plaques on his hips and thighs. Lesions have mild pruritus, expand slowly, and exhibit a trailing white scale on the inner margin.

Histology shows perivascular lymphohistiocytic infiltrate in the superficial dermis with focal spongiosis.

Answer 12

✅ Diagnosis: Erythema Annulare Centrifugum (EAC) — superficial form

✅ Classic infectious trigger to rule out first: Tinea (dermatophyte infection)

✅ Additional associations (as you correctly included):

Viruses: HIV, EBV, VZV

Fungi: Penicillium (e.g. blue cheese)

Drugs: NSAIDs, antimalarials, amitriptyline, rituximab

Other: pregnancy, autoimmune endocrinopathies

Question 13

Deep EAC lesions are associated with trailing white scale and superficial spongiosis.

Answer 13

False

In deep EAC:
* There is no trailing scale
* The epidermis is usually unremarkable
* No spongiosis is present
* Inflammation is deep dermal, with a sharply demarcated perivascular mononuclear infiltrate

Question 14

What is the name of the figurate erythema most strongly associated with paraneoplastic disease, and which internal malignancy is most commonly involved?

Answer 14

Erythema Gyratum Repens

Most common = Lung carcinoma (1/3)

Others: Breast, esophagus, stomach

Question 15

Name two key skin findings in addition to the annular plaques that can be seen in Erythema gyratum repens and support a paraneoplastic process.

Answer 15

Palmaplantar keratoderma

Ichthyosis

Question 16

Erythema marginatum commonly affects the face and is highly pruritic.

Answer 16

False

Does NOT afect the face or palms / soles and is generally assymptomatic

Question 17

A 6-year-old presents with fever, migratory polyarthritis, and a non-pruritic polycyclic erythematous rash on the trunk.
Labs show elevated CRP and a prolonged PR interval.

What is your leading DDx?

Answer 17

Concern for erythema marginatum and Rheumatic Fever.

Jones Criteria:
- joint involvment
- Heart involvement - cariditis
- Nodules (subcutanoeus)
- Erythema marginatum
- Sydenham chorea

Minor: fever, raised inflam markers, prolonged PR interval

Question 18

Which figurate erythema may present with a bull’s-eye appearance and can sometimes vesiculate centrally?

Answer 18

Erythema Migrans

Ass with Lyme disease (90%)

Question 19

What organism causes erythema migrans, and how does it evade early immune clearance? (Name one specific mechanism.)

Answer 19

Borrelia burgdorferi (a spirochete)

Borrelia burgdorferi binds to a tick salivary protein called Salp15, which:
* Shields Borrelia’s outer surface protein C (OspC) from antibody-mediated attack
* Inhibits T-cell activation and adaptive immunity

Question 20

Erythema gyratum repens and erythema annulare centrifugum can both exhibit concentric ring patterns, but EGR spreads significantly faster.

Answer 20

True

Question 21

Name two histologically granulomatous conditions from the differential of annular lesions that may clinically resemble EAC or EGR.

Answer 21

Granuloma Annularae

Sarcoidosis

Question 22

In erythema migrans, Borrelia organisms are found only at the advancing edge of the lesion.

Answer 22

False

At the advancing edge, center, and even deep within the dermis

Their distribution is patchy, reflecting both local proliferation and systemic dissemination

Question 23

A patient presents with annular erythema, mild fever, eosinophilia, and “flame figures” on histology. What is the diagnosis?

Answer 23

Eosinophillic cellulitis (wells syndrome)

Question 24

A 3-month-old infant develops **annular erythematous plaques** that appear, expand, then fade over days. A neutrophilic variant causes purpura and vesicles. What is the umbrella diagnosis for these conditions?

Answer 24

Annular Erythema of Infancy * Appears in infants aged 3–11 months * Lesions: Annular, expanding, fade in days * Neutrophilic variant: May present with purpura, vesicles, even systemic signs Systemic workup:

Question 25

What infiltrate is seen in erythema marginatum histology?

Answer 25

**Perivascular and interstitial infiltrate composed mainly of neutrophils** Occasionally: Eosinophils Extravasated RBCs (in later stages) ❌ No frank vasculitis ❌ Direct immunofluorescence is negative

Question 26

You biopsy an annular lesion with mucin deposition and a CD123+ plasmacytoid dendritic cell infiltrate. What diagnosis should you consider?

Answer 26

✅ LE tumidus ✅ Annular erythema of Sjögren syndrome **CD123+ is a cell surface marker for: 👉 Plasmacytoid Dendritic Cells (pDCs)** A dense dermal infiltrate of CD123+ pDCs is a hallmark of: Lupus erythematosus (esp. tumidus and SCLE) Annular erythema of Sjögren syndrome nterferon-driven dermatoses

Question 27

Which annular dermatosis presents with concentric scaly rings resembling EGR but has dermatophytes on KOH prep?

Answer 27

**Tinea imbricata (a variant of tinea corporis)** Presents with concentric scaly rings — mimicking Erythema Gyratum Repens (EGR) **Caused by: Trichophyton concentricum** Endemic to Southeast Asia, Pacific islands, Central and South America

Question 28

Erythema migrans typically requires multiple tick bites to develop disseminated secondary lesions.

Answer 28

False Secondary lesions occur due to hematogenous and lymphatic dissemination of Borrelia burgdorferi

Question 29

ou biopsy an annular lesion on the face of a middle-aged woman. It shows vacuolar interface change, dermal mucin, periadnexal lymphocytes, and CD123+ plasmacytoid dendritic cells. What diagnosis does this suggest, and what antibody might be positive?

Answer 29

Lupus Tumidus ANA

Question 30

Granuloma annulare, annular sarcoidosis, and EAC all share the histologic feature of mucin in the dermis.

Answer 30

False

Question 31

Which annular dermatosis is classically associated with** IgA monoclonal gammopathy**, and what rare systemic syndrome should be considered?