Histopathological spectrum of Psoriasiform dermatitis

Correspondence: Dr. Jayalakshmy Payippat Leelamma, MD Department of Pathology Government Medical College, Kottayam, Kerala, India E-mail: jayafloyyd@gmail.com Background: Psoriasiform dermatitis is a frequently encountered terminology in a wide variety of inflammatory dermatoses. It often poses challenges to both dermatologists and pathologists alike. Clinical features when considered alone may not be reliable, as they vary with both disease duration and treatment. On the contrary, histopathological material constitutes definite hard evidence, which can be preserved and will continue to be available for future review. The objective of the study is to study the histopathological findings in Psoriasiform dermatitis.

to give a precise diagnosis every time and one relies heavily on clinical correlation. 3However, it is possible to assign specific diagnoses in most cases with a logical and systematic histopathological approach. 3A definitive histopathological diagnosis goes a long way in the treatment of such inflammatory dermatoses.
Major reaction patterns in inflammatory skin disease are Lichenoid reaction, Psoriasiform reaction, Spongiotic reaction, Vesiculo-bullous reaction, Granulomatous reaction and Vasculopathic reaction.The present study lays emphasis on histopathological features of Psoriasiform dermatitis.

MATERIALS AND METHODS
The study was conducted in a tertiary care centre in Kerala, South India, over a period of one year from January 2008 to December 2008.Ethical clearance was obtained from the institutional review committee.All cases of skin biopsy with a clinical diagnosis of Psoriasis or Psoriasis given as one of the differential diagnoses were included in the study.The material included 66 skin biopsies.Patients with a previous diagnosis of the same were excluded from the study.The slides and blocks were retrieved from the archives and multiple serial sections were taken for each biopsy and stained with routine haematoxylin and eosin stain.The important histopathological features observed were subsequently noted on a proforma.The different microscopic features were compared between the cases.Statistical analysis was performed wherever necessary using Excel.

RESULTS
The present study is a comprehensive analysis of 66 cases of PD which constituted 9% of the 590 skin biopsies received at the centre over a period of one years.Age distribution of the study group is given in Table 1.The maximum number of cases of PD, 38 out of 66 (58%), were in the age range of 41-60 years and the least number of cases, 4 out of 66 (6%), were in the youngest age range of < 20 years.In Table 2, the sex distribution pattern revealed that most of the cases of PD, 43 out 66 (65%), were males as compared to females (35%).

DISCUSSION
Histologically, psoriasiform reaction pattern is defined as the presence of epidermal hyperplasia with elongation of rete ridges in a regular manner.The presence of evenly elongated, thin rete ridges with equally long dermal papillae can imply only one condition, i.e., psoriasis. 3All other diseases exhibit an uneven psoriasiform pattern, i.e., rete ridges are of uneven lengths and thickness with thick suprapapillary plates. 3According to Ackerman et al, psoriasiform pattern forms a major subset of perivascular dermatitis, the largest group of inflammatory skin diseases. 4oriasis, the prototype of PD, is a genetically determined, inflammatory and proliferative disease of the skin characterized by dull red, sharply demarcated scaly plaques. 5he two clinical signs, Auspitz's sign and the Grattage test have been described as pathognomonic of psoriasis by Hellgren et al. 6 Regular epidermal hyperplasia, dilated blood vessels in papillary dermis and presence of Munro microabscess and/or Kogoj's abscess have been described to be the most constant or characteristic histopathological features in skin biopsy of psoriasis. 7Similarly, spongiosis, irregular epidermal hyperplasia and absence of Munro micro and Kogoj's abscess have been found consistently in psoriasiform dermatitis. 7stopathological spectrum of Psoriasiform dermatitis         et al 13 also noted parakeratosis, acanthosis, suprapapillary thinning, Munro microabscesses and hypogranulosis in most of the cases.The present study also noted similar histological findings in majority of the cases of psoriasis.Mehta et al 13 stated that, suprapapillary thinning and the absence of granular cell layer could be added to the list of essential histopathological criteria for psoriasis, in addition to Munro microabscess and Kogoj's abscess.
Seven out of 66 cases (60.60%) were that of LSC.Most of the cases, 5 out of 7 (71%), were reported in 41-60 year age group.5 out of 7 cases (71%) were females.According to Lotti et al 14 , LSC is observed more commonly in females compared to males, adults than in children and the microscopic features include stratified squamous epithelium exhibiting orthokeratosis, parakeratosis, acanthosis, and irregular hyperplasia of the rete pegs.The present study also noted similar nonspecific histological findings.
Five cases (7.57%) of PN were observed out of which 4 cases (80%) were in the 40-60 year age group and one case (20%) was in the 41-60 year age group.According to Darshan et al 15 , PN most commonly affects the middleaged and elderly, although it has been seen in young men and children as well.There is no sex predilection but our study had a male preponderance (4 males, 1 female).PN shares some features with both psoriasis and ichthyosis as it demonstrates parakeratotoic hyperkeratosis accompanied by acanthosis and papillomatosis. 15The cases in our study also had histological overlap with psoriasis because of hyperkeratosis, parakeratosis and acanthosis.PRP was diagnosed in 5 patients (2 males, 3 females).Age of onset ranged between 20 and 40 years.Age group, sex and histological features of PRP in our study were comparable to those conducted by Marrouche N et al. 16 Microscopically, follicular plugging in addition to checkerboard alternating orthokeratosis/parakeratosis may serve as clues to PRP diagnosis.
Allergic contact dermatitis was diagnosed in 4 patients (4 females).There was no age predilection.D.L Jovanovi et al 17 states that the value of light microscopic examination in order to differentiate between allergic contact dermatitis and chronic dermatitis is limited and it must be considered together with results of clinical examination and other tests.All four cases in our study had non-specific microscopic features like hyperkeratosis, acanthosis and chronic inflammatory infiltrate in dermis.
Prasad D et al 18 had 3 cases of PR and 2 out of 3 cases were females.All were in 31-40 year age group.In the present study, there were 3 cases of PR and they were observed in 20-40 year age group but all 3 cases were females.Some of the features of PR observed by Prasad D et al were comparable with our study namely absence of granular cell layer, extravasation of red blood cells in papillary dermis and homogenization of papillary collagen.
ILVEN is a distinct variety of keratinocytic epidermal naevus that appears at birth or early childhood, is 4 times more common in girls and has a linear distribution following the Blaschko lines. 19But in the present study, it was seen in 2 males and both were below 5 years of age.
Histopathologic findings in our study were more or less similar to a study by Bandyopadhyay et al 20 with psoriasiform hyperplasia of the epidermis, varying amount of spongiosis, parakeratosis with hypogranulosis alternating with orthokeratosis with hypergranulosis and variable upper dermal perivascular lymphocytic infiltrate.

CONCLUSION
Psoriasis has varied clinical presentations and there is overlap of both clinical patterns and distribution of PD, which often makes clinical diagnosis difficult.Some of the histopathological features are specific and characteristic for each entity like Psoriasis, Pityriasis rubra pilaris, Pityriasis rosea and Inflammatory linear verrucous epidermal nevus whereas some overlap in lesions like Prurigo nodularis, Lichen simplex chronicus and Allergic contact dermatitis.

Histopathological spectrum of Psoriasiform dermatitis
Hence, combination of proper clinical observation and histopathological study will give a conclusive diagnosis.

Table 3 .
The most common diagnosis found on histopathology was Psoriasis.It constituted 40 out of 66 cases (60.60%).Histopathological pattern of Psoriasis is given in Table4.

Table 5 : Comparison of Histoogical features of Psoriasis
8Present studyIn the present study, there were 40 cases of Psoriasis and it was seen commonly above 40 yrs of age, 24 out of 40 cases (60%); this was in accordance with Alexander et al8, who reported psoriasis being common in age group of 41-50 yrs.Thirty out of 40 cases (75%) were males and 10 (25%) were females with male to female ratio of 3:1.Kaur et al 9 , Alexander et al 8 and Yang et al 10 also noted high prevalence in males.Comparison of histopathological features of psoriasis is given in Table 5. Various histopathological studies of psoriasis like Lal et al 11 , Gordon and Johnson 12 and Mehta