Interface and Lichenoid Dermatitis

Question 1

Interface and lichenoid dermatitis classification and ddx always includes ___

Other entities in the differential

Answer 1

Vacuolar vs lichenoid or associated epidermal changes

Drug reactions

Other differential:

1. lichen planus
2. Erythema multiforme and toxic epidermal necrolysis
3. acute GVHD
4. Lupus erythematosus
5. Dermatomyositis
6. Lichen nitidus
7. Lichen sclerosus et atrophicus
8. Perniosis (chilblains)
9. Pityriasis lichenoides et varioliformis acuta (PLEVA) and pityriasis lichenoides chronica (PLC)

Question 2

Lichen planus

Histology

DDX

Answer 2

Histology

1. Band-like infiltrate
2. Acanthosis with overlying orthokeratosis
3. Jagged rete ridges
4. Hypergranulosis
5. Civatte and colloid bodies (dyskeratotic cells)

DDX:

1. Lichenoid (fixed) drug reaction (eos and PK
2. Lupus
3. EM
4. Lichen striatus
5. Lichen planus actinicus

Question 3

EM and TEN

Answer 3

Mild interface inflammation with necrotic keratinocytes prominent or confluent

TEN: full thickness epidermal necrosis (>30% surface area)

Stevens Johnsons has mucosal involvement

Question 4

Acute GVHD

Answer 4

EM-like with

1. vaculoar change
2. Dyskeratotic cells
3. periadnexal infiltrates
4. no/few eos

Question 5

Lupus erythematosis

Types with histology

Answer 5

Discoid LE:

1. Epidermal atrophy
2. interface
3. Superficial and deep perivascular and periadnexal infiltrate of lymphs with PCs
4. Dermal mucin (alcian blue or colloidal Fe +)

Subacute cutaneous LE and systemic SLE:

1. similar to DLE but less infiltrate
2. more vacuolar change
3. apoptotic cells more prominent in SCLE

Question 6

Lupus DIF

Answer 6

Positive “lupus band test”

IgG, IgM, IgA, +/- C3 along basement membrane

Question 7

Dermatomyositis

Answer 7

Histology similar to LE but with milder epidermal atrophy and less inflammation

No deep or periadnexal infiltrates

Less mucin

Question 8

Lichen nitidus

Answer 8

Small papillary dermal collections of lymphocytes (“ball in claw”)

Granulomatous appearance (not true granulomas)

Question 9

Lichen sclerosis et atrophicus

Histology

DDX

Answer 9

Histology

1. Atrophy
2. Papillary dermal edema
3. Collagen sclerosis
4. Follicular plugging

DDX:

1. Radiation dermatitis (perivascular hyalinization and radiation fibroblasts)

Question 10

Perniosis (chilblains)

Answer 10

Acral site

Papillary dermal edema

tight perivascular lymphocytic infiltrates

lymphocytic infiltrates +/- lymphocytic vasculitis

Question 11

Pityriasis lichenoides et varioliformis acuta (PLEVA) and pityriasis lichenoides chronica (PLC)

Histology

DDX

Answer 11

PLEVA:

1. Crusting
2. confluent PK
3. dense wedge-shaped infiltrate
4. RBC extravasation
5. Exocytosis
6. Scattered dyskeratotic cells

PLC

1. Milder infiltrate with interface changes
2. Few dyskeratotic cells
3. Increased pigment incontinence

DDX:

1. Contact derm
2. lupus
3. em
4. drug reaction
5. LyP

Question 12

Interface Differential Chart from Elston

Answer 12