Involucrin in the differential diagnosis between linear psoriasis and inflammatory linear verrucous epidermal nevus: a report of one case.
Bottom Line: Clinical history, physical examination and histopathology analysis may not be sufficient to confirm the diagnosis.We report the case of a 4-year-old girl in which the involucrin immunostaining was helpful in the diagnosis of inflammatory linear verrucous epidermal nevus.Our findings confirm that involucrin immunohistochemistry is a useful tool in such cases.
Affiliation: Federal University of São Paulo, EPM.
Inflammatory linear verrucous epidermal nevus is a variant of verrucous epidermal nevus, characterized by recurrent inflammatory phenomena. Despite well-established clinical manifestations, the differential diagnosis between inflammatory linear verrucous epidermal nevus and linear psoriasis remains difficult. Clinical history, physical examination and histopathology analysis may not be sufficient to confirm the diagnosis. We report the case of a 4-year-old girl in which the involucrin immunostaining was helpful in the diagnosis of inflammatory linear verrucous epidermal nevus. Our findings confirm that involucrin immunohistochemistry is a useful tool in such cases.
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Mentions: ILVEN is a rare skin disease characterized by unilateral lichenoid, verrucous orpsoriasiform lesions. The lesions converge to form plaques and linear bands and may havea clinical resemblance to psoriasis. 4-6 In 1971 Altman and Mehregan definedclinical criteria for the diagnosis of ILVEN: early onset (before 5 years of age in 75%of the cases); 4:1 predominance in females; frequent involvement of the left lowerextremity; pruritus; psoriasiform appearance, following the lines of Blaschko; andpersistent lesions showing marked resistance to treatment. 5 Most cases are sporadic, although familial cases havebeen described. 1 Diagnosis tends tobe particularly difficult in cases that do not fulfill the classic criteria for ILVEN,or in those with both nevoid and psoriatic lesions. Various histopathologic features(acanthosis, papillomatosis, the presence of ortho- and parakeratotic areas, and changesof the papillary dermis) are typically observed in all difficult cases, and are clearlynot useful for diagnosis. 2,7-8In such cases, authors have generally chosen one of three diagnoses: unilateralpsoriasis, ILVEN, or Koebner's phenomenon on a pre-existing epidermal nevus in a subjectwith psoriatic diathesis. 7,9,10-11 Even with meticulous history, detailedclinical examination, including examination of other family members, and close follow-upto observe the progression of the disease, differential diagnosis is sometimesdifficult.2 An objective test todifferentiate between unilateral psoriasis and ILVEN is the pattern of involucrinexpression in the epidermis. Involucrin is a 68 kDa precursor of the cornified envelopethat was originally described by Rice and Green (1979) and ultimately cloned by Eckertand Green (1986). The protein is rod-shaped and includes several reactive glutamineresidues that function in the formation of covalent isopeptide bonds. Involucrin iscross-linked early in cornified envelope formation and forms a scaffold forincorporation of other precursors. Involucrin expression initiates in the early spinouslayer and is maintained in the granular layer. In the transition zone, involucrin isincorporated via the action of transglutaminase as a component of the cornifiedenvelope. 12 In the normal epidermisit is present in the upper part of the squamous cell layer and in the granular layer,but in psoriasis it is detectable at deeper levels, from the suprabasal keratinocytesupwards (Figures 4 and 5). 13-15 Ito and colleagues showed that in ILVENthe involucrin expression is increased in orthokeratotic regions but is deficient inparakeratotic regions; by contrast, in parakeratotic areas of psoriasis, most suprabasalkeratinocytes express involucrin. 3,7 Other authors have suggested that thebehavior of other markers (elastin, antikeratin 10, antikeratin 16, Ki-67) may be usefulto differentiate between unilateral psoriasis and ILVEN. 6,8 Differentiationbetween ILVEN and unilateral psoriasis is clearly important since the two disordersrespond to treatment in different ways. Our case represents a situation where theclinical and histologic features were unable to make the definitive diagnosis betweenlinear psoriasis and ILVEN, but the study of involucrin could give us a further clue,thereby helping to establish a more accurate diagnosis with a better chance of aneffective therapeutic management of the disorder.