Indian Journal of Dermatology
: 2006  |  Volume : 51  |  Issue : 4  |  Page : 296--297

Linear psoriasis responding to short contact dithranol and topical steroid

NB Dhanya, Shanmuga V Sundaram, Karthick S Prabhu, Reena Rai, CR Srinivas 
 Dept. of Dermatology, PSG Hospitals, Peelamedu, Coimbatore - 641004.Tamil Nadu, India

Correspondence Address:
C R Srinivas
Dept. of Dermatology, PSG Hospitals, Peelamedu, Coimbatore - 641004.Tamil Nadu

How to cite this article:
Dhanya N B, Sundaram SV, Prabhu KS, Rai R, Srinivas C R. Linear psoriasis responding to short contact dithranol and topical steroid.Indian J Dermatol 2006;51:296-297

How to cite this URL:
Dhanya N B, Sundaram SV, Prabhu KS, Rai R, Srinivas C R. Linear psoriasis responding to short contact dithranol and topical steroid. Indian J Dermatol [serial online] 2006 [cited 2021 Dec 3 ];51:296-297
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Full Text

Psoriasis is a chronic inflammatory disease characterized by erythematous scaly plaques on the extensor aspect of the body. Unusual localization and atypical presentations of this disease are frequently encountered. Unilateral psoriasis arranged linearly or along Blaschko lines in the absence of typical lesions elsewhere in the body is uncommon[1] and is confused clinically and histopathologically with verrucous epidermal naevus.[2] We report a case of linear psoriasis responding to topical short contact dithranol and topical steroid.

A 38-year-old male presented with linear erythematous scaly lesion of the right upper limb of 10 years duration. The lesions started over right middle finger and spread to involve the hand, forearm and arm up to the shoulder in a linear patter. On examination, well-defined erythematous scaly papules and plaques were seen extending from the dorsum of the middle finger to the shoulder in a linear pattern. The nail on the corresponding middle finger showed linear ridges. No other skin lesions were present elsewhere on the body. Clinical diagnosis of linear Psoriasis with a differential diagnosis of ILVEN was made.

Histopathology revealed hyperkeratosis, focal parakeratosis and a collection of neutrophils in the Stratum corneum. Cup-shaped depression in the epidermis and regular acanthosis with club-shaped rete ridges were seen. A peri-vascular lymphocytic infiltrate was present in the superficial dermis.

The histopathology showed features of both Psoriasis and ILVEN. We empirically treated the patient for Psoriasis with topical steroids and keratolytics for six months, methotrexate 7.5 mg weekly once for four months and tazarotene for two months without significant improvement.

Since he did not improve with the treatment, he was advised short contact therapy with dithranol 1.15%, salicylic acid 1.15%, solution of coal tar 5.3% for one hour and (which was wiped with liquid paraffin) followed by application of topical clobetosol propionate cream 0.05%. After two months, the lesion had resolved with minimal pigmentation, lichenification and scaling.


Linear psoriasis is a rare form of psoriasis and is characterized by linear distribution of psoriatic lesion along the Blaschko Line. There is controversy regarding linear psoriasis as a separate entity and many consider it as ILVEN.[3] Pathogenesis of linear psoriasis is unclear but it could be explained as a result of the migration of cells harboring somatic mutation following the lines of Blaschko during early embryogenesis.[4]

Although ILVEN may be present from birth it is reported to occur in early childhood, during puberty and in early adulthood.[5] Lesions are present as linear verrucous plaques on the leg, pelvis and buttock. Diagnostic criteria in ILVEN include the early age of onset, female predominance, frequent left lower extremity involvement, pruritis classical biopsy findings and lesional persistence with refractoriness to treatment.[5]

Inflammatory linear verrucous epidermal naevus and unilateral linear lesions of psoriasis overlap.[6] Involucrin expression in the parakeratotic epidermis distinguishes psoriasis from inflammatory linear verrucous epidermal naevus.[7] Assessment of elastase positive cells and that of keratin - 16 and keratin - 10 provide additional diagnostic impact in differentiating inflammatory linear verrucous epidermal naevus from linear psoriasis.[2]

Patients presenting with unilateral, localized psoriasis should be examined thoroughly to find out lesions of psoriasis elsewhere. However in our case, the lesions have responded to topical dithranol therapy and steroid, which is effective in psoriasis but had failed to respond to other anti-psoriatic treatment. It has been considered that linear psoriasis represents either ILVEN in a patient with psoriasis, a naevus,[2],[8] or even an invasion of a linear epidermal naevus by psoriasis as a manifestation of the isomorphic reaction.[4]


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