Linear psoriasis is an unusual clinical variation of psoriasis that manifests segmentally along the lines of Blaschko. A major differential diagnosis is inflammatory linear verrucous epidermal nevus (ILVEN). The treatment of linear psoriasis is often challenging, with inadequate response to biological agents reported in the literature. We report a case of a 25-year-old African-American female who presented with asymptomatic hyperkeratotic papules along the lines of Blaschko and was subsequently diagnosed with linear psoriasis. After failing conventional treatment regimens, the patient received a trial of ixekizumab with complete resolution of cutaneous lesions reported after 4 months and only 8 doses of the anti-IL-17 biologic agent.
Linear psoriasis is a rare clinical variation of psoriasis that manifests segmentally along the lines of Blaschko. The pathogenesis remains unclear, though some have proposed it could be explained by the well-established concept of genetic mosaicism [
A 25-year-old African-American female presented to our clinic with asymptomatic lesions linearly arranged over her left upper extremity. The initial lesion first appeared fifteen years ago and new lesions gradually appeared over time. She denied joint pain and/or a history of infections prior to lesion development. Her past medical history was significant only for posttraumatic distress disorder and depression. There was no personal or family history of psoriasis or other dermatologic disease. Prior to presentation in our clinic, she had a skin biopsy of the right forearm which showed chronic spongiotic dermatitis with parakeratotic foci and superficial perivascular mononuclear infiltrates. No deep dermal or periadnexal infiltrates were seen and periodic acid-Schiff staining was negative for fungal organisms. Based on the results, both lichen striatus and linear psoriasis were considered as potential diagnosis, and she was started on high-potency topical steroids. A month later, the patient was referred to our clinic when she failed to respond to treatment.
Physical examination revealed hyperkeratotic and scaly gray papules coalescing into a linear plaque of the right dorsal fifth finger extending medially to the right elbow (Figure
(a) Linearly arranged hyperkeratotic and scaly gray papules on the right fifth finger and dorsum of the hand extending to the right elbow. (b) Multiple hyperkeratotic papules present within a tattoo on the posterior right arm.
(a) Histopathological slides. At 2x magnification there is parakeratosis and epidermal acanthosis. (b) Histopathological slides. At 10x magnification a regularly acanthotic epidermis with hyperkeratosis alternating with parakeratosis. Rete ridges show psoriasiform hyperplasia.
(a) Close-up of lesions present on right fifth finger and dorsum of hand. At two-week follow-up, new papules appear in the area that is previously electrodessicated (black arrow). (b) Remarkable clearing of the lesions and postinflammatory hypopigmentary changes can be seen after 8 doses of ixekizumab. (c) Psoriatic lesions are no longer present on the tattoo after treatment with 8 doses of ixekizumab.
Linear psoriasis is a rare clinical presentation of psoriasis characterized by the linear distribution of psoriatic lesions along the lines of Blaschko. The main differential diagnosis is ILVEN. Gross morphological distinction between these two entities is difficult. Furthermore, the two entities share similar histological findings and the coexistence of ILVEN and psoriasis has also been reported [
We are now able to conclude that linear psoriasis was the correct diagnosis in this case based on several observations. First, our patient’s lesions were nonpruritic, and ILVEN tends to be more pruritic than psoriatic lesions [
It is known from a small number of reports that segmental manifestations of psoriasis respond less favorably to systemic therapies such as methotrexate, acitretin, and, more recently, biologics [
Summary of reported cases of linear psoriasis treated with a biological agent.
Authors (year) | Gender | Age | Distribution of linear psoriasis (LP) | Other features | Biological agent used and outcome |
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Colombo et al. (2011) [ |
Male | 67 years | Middle of ventral trunk and left side of arm, hand, thigh, knee, and tibia | Psoriatic arthritis and diffuse plaque psoriasis. Failed to respond to acitretin, cyclosporine, and methotrexate | Plaque psoriasis responded to |
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Rott et al. (2007) [ |
Male | 11 years | Left side of the body | Psoriatic arthritis, nail changes. Failed methotrexate, cyclosporine and etanercept | Psoriatic arthritis responded to |
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Sfia et al. (2009) [ |
Male | 29 years | Left arm and left leg | Additional psoriatic plaques on the body | Psoriatic plaques responded to |
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Arnold et al. (2010) [ |
Male | 50 years | Left flank | Diffuse plaque psoriasis. Failed to respond to topical steroids, PUVA, UVB, cyclosporine, and etanercept | Plaque psoriasis responded to |
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Weng and Tsai (2017) [ |
Male | 27 years | Right upper arm, shoulder, and back | In addition to plaque psoriasis. Failed to respond to methotrexate, acitretin, topical vitamin D3 analogs and steroids | Plaque psoriasis responded to |
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Ghoneim et al. (2017) | Female | 25 years | Dorsum of right hand, forearm and arm, and suprapubic region, left thigh and occiput | Failed topical high-potency steroids | Linear psoriasis responded favorably to 8 doses of |
The authors declare that there are no conflicts of interest regarding the publication of this paper.