Lichenoid Disorders

Question 1

Lichen striatus

Answer 1

CLINICAL FEATURES
Self limiting
Asymptomatic, may be itchy in adults
Children
F > M

Sudden onset
Maximum extent within 2-3 weeks
Gradual extension can continue for months
Pink or red flat topped papules in a linear distribution in the lines of Blaschko
Coalesce into dull red-brown slightly scaly linear band —> sometimes broaden into plaques
Few cm in length vs extend entire length of the limb
May be continuous vs interrupted
Occur as isolated lesions on the limbs (1 arm or leg, sometimes neck, trunk) in children 5-15 years
+/- nail involvement —> longitudinal ridging, splitting, onycholysis, nail loss

COMPARISON WITH LINEAR LP
Not violaceous in colour
No umbilication
No wickham striae

CLINICAL VARIANTS
Parallel linear bands/zosteriform patterns (dermatomal)
Extensive bilateral lesions (exceptional)
Repeated episodes in different locations

AETIOLOGY/CAUSE
Incompletely understood
? Atopy —> 40% of cases have background of atopy
? Infectious agent, possibly a virus —> clustering of cases in families and in winter

ENVIRONMENTAL FACTORS/TRIGGERS
Infectious agents 
- Viral —> cases in cold season, prodromal viral symptoms)
- VZV infection
MMR vaccination
Skin Trauma

ASSOCIATED DISEASES
Atopy

PATHOGENESIS
? Post-zygotic mutation or loss of heterozygosity —> cutaneous antigenic (temporary phenomenon) mosaicism —> predisposing to effects of an environmental trigger/infectious agent —> blaschkoid

DDX (pink —> red-brown papules)
Linear psoriasis
Linear Darier disease
Linear LP
Linear porokeratosis
ILVEN (Inflammatory linear verrucous epidermal naevus) —> always itchy, persists despite periods of improvement

DDX (linear hypopigmented streak)
Linear vitiligo
Hypomelanosis of Ito

IX
Skin bx may be helpful

HISTO
Variable
Depends on stage of disease
Band-like infiltrate composed of lymphocytes, histiocytes including dense perivascular and periadnexal with deep extension
Focal liquefactive degeneration of the basal layer
Overlying epidermal change including parakeratosis, hyperkeratosis (resembling LP)
Spongiosis (early change)
Dermal oedema
+/- acanthosis
+/- dyskeratosis (corps and ronds) 50% of cases
IHC —> predominance of CD 8 + T cells

MX
No Rx necessary if asymptomatic (usually children) as largely self limiting —> observation, reassurance
Active Rx for patients (usually adults) with itch

TOPICALS skin lesions
TCS (first line)
TCI i.e. tacrolimus, pimecrolimus if skin atrophy is a concern (second line)

TOPICALS nail involvement
Potent TCS cream under occlusion

PDT for skin lesions (third line)

COURSE/PROGNOSIS
Variable
Typically Resolves over 6-12 months
Sometimes lasts > 1 year
Sometimes relapsing course (esp adults)

COMPLICATIONS
Post-inflammatory hypopigmentation or hyperpigmentation (rarer) may occur and persist for years

Question 2

Lichen planus

Answer 2

Idiopathic

Skin, mucosa

Question 3

LP variant - Mucosal LP

Answer 3

Lesions comfined to the mouth

Question 4

LP variant - Lichen planopilaris

Answer 4

Hair follicles

Question 5

LP variant - Hypertrophic LP

Answer 5

Develops during the course of a subacute attack

Question 6

LP variant - LP of the palms and soles

Answer 6

Firm to the touch

Yellow in hue

Question 7

LP variant - Actinic LP

Answer 7

Children, young adults with dark skin living in tropical countries

Question 8

LP variant - LP pigmentosus

Answer 8

Pigmentary disorder in India, Middle East

Question 9

LP variant - Annular LP

Answer 9

Few large annular lesions

Question 10

LP variant - Bullous LP and LP pemphigoides

Answer 10

BULLOUS LP

LP PEMPHIGOIDES

Question 11

LP variant - Lichen nitidus

Answer 11

CLINICAL FEATURES
Rare
Children or young adults

Pinpoint to pin head-sized papules
Flesh-coloured
Flat or dome-shaped
shiny surface
Usually discrete, may be closely grouped

Usually asymptomatic, but can be intensely itchy

Koebner phenomenon i.e. lesions along scratch marks

Sites of predilection -

• Forearms
• Penis
• Chest
• Abdomen
• Buttocks

Nail involvement -

• Pitting
• Rough nails
• Longitudinal ridging

But can be found anywhere on the body including:
Palms and soles -
- Confluent hyperkeratosis resembling chronic fissured eczema VS
- Multiple distinctive minute papules —> purpuric —> resemble pompholyx
Mucous membrane

VARIANTS
Generalised
Linear
Actinic

DDX
Lichen scrofulosorum (follicular papules small patches on the trunk)
KP (horny follicular papules extensor surface limbs)

ASSOCIATED DISEASES
LP
Crohn disease
Trisomy 21
Congenital megacolon
Niemann-Pick disease

IX
Skin bx

HISTO
Well circumscribed intense infiltrate in the dermis immediately below epidermis
Rete ridges at the margin of the infiltrate elongated and tend to encircle it (ball and clutch)
Lymphocytes, histiocytes +/- Langhan’s giant cells +/- plasma cells
Overlying epidermis flattened, parakeratosis cap
Sometimes liquefaction degeneration of the basal layer

MX
No Rx in most cases (asymptomatic, self limiting)

TOPICALS if desired i.e. on the penis
TCS

PHOTOTHERAPY
Heliotherapy
NbUVB
PUVA

SYSTEMICS
Acitretin (palmoplantar involvement)
Astemizole (generalised variant)

COURSE/PROGNOSIS
Self limiting

Question 12

LP variant - Nekam disease

Answer 12

Rare

Question 13

OTher LP variants

Answer 13

GUTTATE LP

ACUTE AND SUBACUTE LP WITH CONFLUENCE OF LESIONS

MIXED LP/DLE DISEASE PATTERNS