The differential diagnosis included linear psoriasis and ILVEN. The isomorphic reaction seen within the patient's tattoo (Koebner phenomenon) favored a diagnosis of psoriasis.
The main differential diagnosis is ILVEN. Gross morphological distinction between these two entities is difficult.
First, our patient's lesions were nonpruritic, and ILVEN tends to be more pruritic than psoriatic lesions .
(3) In addition to the syndromes described, there are reports of associations between keratinocytic nevi and ILVEN
with hypophosphatemic rickets and precocious puberty.
Some consider linear psoriasis to be either synonymous with inflammatory linear verrucous epidermal nevus (ILVEN) or an invasion of pre-existing epidermal nevus by psoriasis due to koebnerisation.3,4 In our case the lesions clinically looked like ILVEN but histopathology was consistent with psoriasis.
These features were absent in our patient so we ruled out ILVEN. Further clues supporting the diagnosis of psoriasis for this patient included the lack of pruritus, a good response to acetretin, and the histopathology which was consistent with psoriasis.
In conclusion we believe that linear psoriasis is a distinct entity and can turn into pustular form and can mimic ILVEN.
The lesion clinically looked like ILVEN
but histopathology was consistent with psoriasis.