MEDICAL ILLUSTRATION
Unilateral Lichen Planus Along the Lines of Blaschko:
a Rare Clinical Presentation
Sanjeev Gupta1, Sunita Gupta2, Mary Thomas3, Aneet Mahendra1
1
Department of Dermatology and STI, MM Institute of Medical Sciences and Research. Near Shiv Mandir,
No. B-2 Mullana, Ambala, India. Correspondence mail: [email protected].
2
3
Department of Medicine, MM Medical College Residential Campus. Mullana Ambala Haryana, India 133203.
Consultant Dermatologist Bangalore India.
Figure 1.
Figure 2.
Figure 3.
A 34 year man presented to us with itchy
lesions on one half of the trunk for the past two
months. The lesions started as erythematous to
violaceous papules and plaques on the flank and
gradually increased in number to involve the left
side of the trunk (Figure 1 and 2). Some areas
showed the Koebner phenomenon. These lesions
were distributed along the lines of Blaschko.
Examination of the oral mucosa and nails was
within normal limits. There was no history of drug
intake, or topical applications prior to the onset
of the lesions. He did not have any other known
co-morbidities. A differential diagnosis of lichen
striatus, lichenoid herpes zoster, linear epidermal
nevus and linear psoriasis was considered. A
routine hemogram liver function tests and thyroid
function tests were normal. Serological tests
for hepatitis B, hepatitis C, HIV and syphilis
were negative. A skin biopsy was performed
which showed hyperkeratosis, acanthosis,
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Sanjeev Gupta
band like lymphocytic dermal inflammatory
infiltrate along the basement membrane with
basal cell degeneration, colloid bodies in the
upper dermis and melanin incontinence. These
features were consistent with a diagnosis of
lichen planus (LP). Immunoflorescence was
not performed due to lack of availability.
In view of the clinical features, evidence of
koebnerisation and histopathology, a diagnosis of
Blaschkoid LP was made. The patient was treated
with topical steroids and oral antihistaminics
with gradual resolution of the lesions with
hyperpigmentation. The lines of Blaschko are
thought to result from a form of mosaicism.
Many genetic as well as acquired dermatoses
have been seen to follow the pattern dermatoses
e.g.nevi, incontinentia pigmentii, vitiligo and
scleroderma.1 Lichen planus following the lines
of Blaschko is rare. Less than 0.5% of patients
with LP present with Blaschkoid LP.2 It has been
reported more commonly in children though it
can also occur in adults. Clinically, the patient
presents with the classical lesions of LP in a
linear distribution, usually on the limbs and
trunk though other areas of the body may also
be involved. Few non segmental lesions may
occur and koebnersitaion may also be observed.
Histologically, it is characterized by a bandlike
infiltrate of lymphocytes and histiocytes with
destruction of the basal ayer with degenerative
keratinocytes in the lower epidermis. 3 The
etiology of Blaschkoid LP is unknown, however
it has been thought to be due to an abnormal
keratinocyte clone that is only unmasked after
the initiating event for lichen planus.4
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The differential diagnosis of Blaschkoid LP
includes epidermal nevi, linear psoriasis, linear
porokeratosis, linear darriers disease and lichen
striatus. Histological examination is a useful tool
to differentiate between these conditions.5,6 It
should also be differentiated from its close mimic,
zosteriform LP which occurs in a dermatomal
pattern and may occasionally be confused with
the Blaschkoid LP.3
The course of Blaschkoid LP is usually
benign and self-limited. Though linear LP has
been seen in association with hepatitis C and
metastatic carcinoma 7, no such associations
have been documented with the Blaschkoid
varient. Lesions respond to topical potent
steroids and oral antihistamines and heal with
hyperpigmentation as in classical LP which may
persist for long durations.2
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