Histology of psoriatic erythroderma in infants: analytical study of eight cases.

BACKGROUND: Erythroderma in infants is a rare condition of varied etiology. Psoriasis is now emerging as the most common cause of erythroderma in infants. Early diagnosis of the etiological cause much depends upon the histological confirmation, which is essential for an early and appropriate treatment. AIM: It was aimed to study the histological findings in psoriatic erythroderma in infants.
MATERIALS AND METHODS: A total of 8 infants up to 1 year of age presenting with erythroderma, clinically suspected to be of psoriatic etiology attending private clinic were included. After detailed history taking and astute clinical exam, all of them were biopsied. In case 6, with a positive family history of psoriasis and asthma in parents, biopsy was taken from two sites. The histological findings of all nine biopsies were studied and analyzed.
RESULTS: Histology of all eight children showed psoriasi form pattern with acanthosis (AC) and dilated papillary capillaries (PC). Spongiform (SF) pattern was seen in the second biopsy (6b) of child with features of both psoriasis and atopy. SF pustule of Kogoj or Munro's abscess was not seen in any of them.
CONCLUSION: Regular AC and PC dilatation were the consistent histological findings observed in infants with erythrodermic psoriasis. These were the early findings observed in younger infants. Co-existence of psoriasis with atopic dermatitis may indicate a common pathogenic mechanism or an immunogenetic spin-off.

What was known?

Erythroderma in infants can be due to psoriasis and histological diagnosis can be delayed up to the 11th month of the life.

Introduction

The term, erythroderma, designates a generalized erythema of the skin usually associated with exfoliation. The etiological diagnosis of eryhroderma in infants is often a challenge. Recent studies indicate that psoriasis contributes to nearly a third of erythroderma in neonates and infants.[1] The erythrodermic form occurs in about 1.4% of psoriasis cases in children and adolescents.[2] Over all less than 3% of childhood psoriasis manifests with erythroderma.[3] The histological confirmation of the cause is important in the management and follow-up of infants with erythroderma.

Materials and Methods

Eight infants with erythroderma, clinically suspected to be of psoriatic etiology were included. A family history was elicited in all with reference to psoriasis, atopic dermatitis and ichthyosis to aid the diagnosis. A thorough clinical examination was performed. Biopsy was taken from all infants and six serial sections were made out of each biopsy specimen. In one infant (case 6) whose father was a psoriatic and mother an asthmatic biopsy was done from two sites, trunk (6a) and leg (6b). The histological findings of nine biopsies were analyzed in two steps and reported.

Step I was to grossly note the pattern and Step II to study the finer details.

In Step I, the findings were divided in to three major patterns namely psoriasi form (PF), spongiform (SF) and ichthyosiform based on the following criteria.[1]

PF pattern

PF epidermal hyperplasia (confluent parakeratosis (PK), hyperkeratosis (HK), hypogranulosis, suprapapillary thinning of the epidermis, regular acanthosis (AC) often with clubbed rete ridges).

PK.

None or mild spongiosis.

SF pattern

Eczematiform epidermal hyperplasia (focal edematous PK, AC or HK, spongiosis, sometimes spongiotic vesicles).

Ortho or PK.

Mild or intense spongiosis.

Mild or intense lymphocyte exocytosis.

Ichthyosiform pattern

Ichthyosiform epidermal hyperplasia (compact orthohyperkeratosis, normal or thickened granular layer (GL), follicular ostial plugs).

Orthokeratosis.

No or few inflammatory cells.

In Step II following aspects were studied and analyzed:

Stratum corneum – HK; PK; orthokeratosis.

Stratum granulosum – normal; attenuated; accentuated.

Neutrophil collection – mild, SF pustule of Kogoj; Munro micro abscess.

Squamous layer – normal; acanthotic; spongiotic.

Rete – regular; irregular; clubbing.

Keratinocyte necrosis in the epidermis – absent; present.

Papillary vasculature – capillary dilatation.

Dermal infiltrate (DI):

Cell type – lymphocytic; eosinophilic; mixed.

Density – none; mild; intense.

Observations

Case 1 [Figure 1] was a 5-day-old newborn, the youngest of the cases analyzed. Biopsy of eight infants showed PF pattern. The second biopsy of case 6 [Figure 2] showed SF pattern (6b) while biopsy from the trunk of the same infant showed a PF pattern (6a). Histopathological findings in all infants with PF pattern showed regular AC, dilated papillary capillaries (PC). Except case 4 all showed attenuation of GL. Strikingly none of them showed SF pustule or Munro micro abscess. However, two of them, case 5 and 8 who were 8 and 11 month old infants respectively showed neutrophilc infiltrate above the supra papillary thinning. In case 6, the second biopsy, 6b taken from the leg showed SF pattern with spongiosis, irregular AC and mixed DI. The overall observation of all nine biopsies is given in Table 1.

Figure 1

Histology with H and E, ×200 (case 1) under high power showing regular acanthosis, dilated papillary capillary with suprapapillary thinning

Figure 2

(a) Histology with H and E, ×40 (case 6) showing regular psoriasiform acanthosis and papillary capillary dilatation, (b) Histology with H and E, ×40 (case 6) showing spongiosis, irregular acanthosis and lymphocytic infiltrate in the dermis

Table 1

Histological findings in eight infants with psoriatic erythroderma

Discussion

Keratinocyte proliferation and vascular changes are important microscopic findings in the early evolution of psoriasis. AC is probably due to an increase in the number of cycling cells rather than reduction in the cell cycle time. There is approximately seven fold increase in the number of such proliferating cells.[4] It is worth noting that increased numbers of proliferating keratinocytes are also seen in atopic dermatitis. In psoriasis, multiple growth factors, present in lesional skin are capable of modulating keratinocyte proliferation. Transforming growth factor-α appears to be an important autocrine mediator that modulates the inflammation.[5]

With regard to vascular changes, there is dilatation and elongation of capillary loops with the increase in the endothelium of superficial microvasculature.[6] Theses findings point toward the importance of angiogenesis, in the pathogenesis of psoriasis. It is interesting to note that the epidermal keratinocytes are the primary source of angiogenic activity.[7] They produce soluble mediators including vascular endothelial growth factor (VEGF) having angiogenic activity, which is over-expressed in psoriatic epidermis. Many studies point to a primary role for the immune system in the pathogenesis of psoriasis. However, it cannot be ruled out that vascular change precedes the immune response.[8] Some patients with erythrodermic or severe plaque psoriasis have evidence of systemic capillary leak such as proteinuria. In such patients, circulating VEGF is detectable and correlates with proteinuria,[9] a well-known complication of erythroderma. Dermal capillaries in addition to vascular growth, contribute to the inflammatory process. There is induction of eselectin and up-regulation of intercellular adhesion molecule-1 that lead to accumulation of skin homing T lymphocytes within lesional skin.[10]

The above pathogenic mechanisms perhaps are best reflected in the histology as very early changes of psoriasis in our cases where all the cases showed regular AC and PC dilatation with sparse DI.

Conclusion

When psoriasis presents in infants the evolution of the disease is yet to take a fully formed clinical picture. More so in case of erythroderma where the infant presents with generalized erythema and scaling and an established psoriatic plaque is not frequently seen. Keratinocyte proliferation and vascular changes are the early features of erythrodermic psoriasis in infants. Regular AC and PC dilatation, the two consistent histological findings observed in this study, will give a clue to an early diagnosis of psoriasis in infants. Co-existence of psoriasis with atopic dermatitis may indicate an immunogenetic spin-off. Further genetic evaluation and immunohistochemistry will through more light in predicting the evolution of the disease and thereby a better management.

What is new?

Regular AC and capillary dilatation are the early histological findings of erythrodermic psoriasis in infants.

Munro micro abscess and SF pustule of Kogoj are not mandatory for the diagnosis of infantile erythrodermic psoriasis.

Clinicopathological co-existence of psoriasis and atopy in infantile erythroderma.