Eczema pathology

Introduction

Eczema It is a common skin condition with multiple clinical patterns, characterized histologically for spongy tissue reaction pattern. The terms eczema and dermatitis are often used interchangeably to denote a polymorphic inflammatory reaction pattern involving the epidermis and dermis. However, 'dermatitis' means inflammation of the skin and is not synonymous with eczematous processes. The consensus among most dermatopathologists is that the term 'eczema' should be replaced by the term 'spongiotic dermatitis' to reflect the histopathological changes underlying the so-called 'eczema'.

Histology eczema

The spongiotic tissue reaction pattern is characterized by intercellular. edema inside the epidermisspongiosis) Initially, there is an enlargement of the intercellular spaces between keratinocytes and lengthening of intercellular bridges. Increased accumulation of fluid leads to the formation of intraepidermal vesicles. Spongiotic dermatitis is a dynamic disease process; vesicles come and go and can be located at different levels of the epidermis. Infiltration of the epidermis with lymphocytes (exocytosis) It is common. Parakeratosis it forms above the areas of spongiosis, probably as a result of an acceleration in the movement of keratinocytes towards the surface. Drops plasma accumulate in the mounds of parakeratosis. Dermal changes include varying degrees of edema and a superficial effect perivascular infiltrate with lymphocytes, histiocytes and occasional neutrophils and eosinophils.

Three stages of eczema.

Clinically, eczema is grouped according to etiology. Histologically, it is more useful to classify eczema according to chronicity. Histologically, there are three stages of eczema: acute, subacute and chronic. An eczematous disease can start at any stage and progress to another.

Acute eczema

Acute spongiosis is characterized by massive intercellular edema of the epidermis with widening of the intercellular spaces, disruption of desmosomes and microvesicle formation. Although vesicles are usually intraepidermal, with sufficient vesiculation, they can become subepidermal. The vesicles are filled with protein fluid containing lymphocytes and histiocytes (Figure 1, arrow). In allergic / contact dermatitis, eosinophils may be prominent (eosinophilic spongiosis).

Subacute eczema

This is the most common type of spongiotic dermatitis. The degree of spongiosis and exocytosis of inflammatory cells is mild to moderate. Irregular acanthosis and parakeratosis are additional features compared to acute spongiotic dermatitis. A superficial dermal perivascular lymphohistiocytic inflammatory infiltrate, swelling of endothelial papillary dermal edema and cells are present (Figure 2).

Chronic eczema

In chronic spongiotic dermatitis, the degree of spongiosis is often mild and difficult to appreciate. Vesiculation is rare. There is significant epidermal acanthosis, which can show a psoriasiform pattern with hyperkeratosis, hypergranulosis and minimal parakeratosis. Fibrosis of the papillary dermis may be present (figure 3).

Types of eczema

Atopic dermatitis

Atopic dermatitis is a common skin condition, particularly in children, and is associated with a personal and family history of atopy. Although acute and subacute spongiotic patterns have been described in atopic dermatitis, they are much less common than chronic spongiosis. Interestingly, a follicular not uncommon pattern showing spongiosis of the infundibular A portion of follicles and a scarce dermal infiltrate (figure 4, the arrow shows follicular spongiosis). The follicular pattern is more often found in more depth pigmented cutaneous phototypes

Irritating contact dermatitis

Irritant contact dermatitis is caused by contact with water, detergents, and other chemicals, and subsequently occurs more frequently on the hands. The histology of irritant contact dermatitis is typically mild spongiosis, epidermal cells. necrosisand neutrophilic infiltration of the epidermis. Figure 5 shows an early injury with infiltration of the epidermis by neutrophils. Figure 6 shows a more acute and severe example with full thickness necrosis.

Allergic contact dermatitis

Allergic contact dermatitis occurs when there is sensitization to a generally tolerated environmental contact such as nickel, fragrance, hair dye or preservatives. A pattern of subacute, chronic, or acute dermatitis can be seen. The dermal inflammatory infiltrate contains predominantly lymphocytes and other mononuclear cells (Figure 7). Allergic contact dermatitis occasionally causes atypical T cell infiltrators which can simulate mycosis fungoides.

Discoid eczema

Discoid eczema or nummular dermatitis is a particularly chronic eczema characterized clinically by papules or papulovesicles which get together in coin-shaped patches. Histological Changes vary with chronicity. Early lesions show moderate spongiosis with mild acanthosis and exocytosis of inflammatory cells. Over time, the degree of acanthosis increases. Additional features include scale–Cortex formation over the thickened epidermis and dermal perivascular inflammatory infiltrate. Usually it is wise to make special stains to exclude a fungus infection (tinea corporis)

Stasis dermatitis

Stasis dermatitis is a common condition that affects the secondary legs of people with disabilities. venous circulation. Spongiosis is usually mild with foci of parakeratosis and scaly crusts. Ulceration It is a common complication. Dermal changes are prominent with neovascularization, hemosmosin statement and varying degrees of fibrosis (depending on chronicity).

Seborrheic dermatitis

Seborrheic dermatitis occurs most frequently on the scalp and face secondary to toxic Yeast produced substances. Histologically there is a spongiosis that can be acute, subacute or chronic depending on the biopsy of the lesion. Spongiosis may have an overlying bark area and is often found on hair. follicle (figure 8). Presence of neutrophils within the epidermis or stratum corneum should provoke further examination of yeast with PAS staining. More chronic injuries show progressive psoriasiform hyperplasia of the epidermis with less spongiosis. Dermal changes include mild edema of the papillary dermis with a mild superficial perivascular infiltrate of lymphocytes, histiocytes, and neutrophils.

Asteatotic eczema

Asteototic eczema develops as a result of very dry skin. It is more common in the elderly and in the lower extremities. Histologically, the most common finding is mild subacute spongiotic dermatitis. The stratum corneum is compact and slightly irregular (Figure 9).

Go reaction

Id reaction or autoeczematisation describes the appearance of generalized eczema in response to a located skin disease or infection at a distant site. Clinically the reaction of Id is polymorphous including pompholyx-like reactions affecting the hands and feet or more generalized papular rashes. The histology of the id reaction often mimics that of initially localized dermatosis or shows a spongiotic reaction pattern with varying intensity. Mild dermal edema and lymphocytic infiltrations are reported.

Lichen simplex

Lichen simplex is a type of neurodermatitis characterized by areas of thickening of the skin in response to repeated scratching or rubbing. Histologically, there is marked hyperkeratosis, hypergranulosis, and occasional small foci of parakeratosis. The epidermal ridges are elongated and irregularly thickened. Mild spongiosis is variably present depending on the cause. Papillary dermal fibrosis is a characteristic feature (Figure 10).

Nodular prurigo

Prurigo nodularis is a severe itchy skin condition of unknown etiology, characterized by firm, itchy bumps. Histologically, there is an increase in acanthosis compared to lichen simplex, orthohyperkeratosis, and hypergranulosis. The areas of acanthosis and dilated follicles form a discreet mass that can be seen histologically (Figure 11). Mild spongiosis and parakeratosis are occasional features. Lesions often erode as a result of excoriation, and there may be minor changes marked to mimic a scaly carcinoma. Dermal changes include vascular hyperplasia, perivascular inflammatory infiltrate (consisting predominantly of lymphocytes, histiocytes, and plasma cells), and fibrosis of the papillary dermis (Figure 12).

Vesicular hand dermatitis

Acral the skin can be easily identified histologically due to the thickness of the stratum corneum and the absence of follicular structures. The acute form of vesicular dermatitis of the hand is characterized by intraepidermal spondiotic vesicles or bullas. The epidermal thickness is normal (figure 13). In chronic hand dermatitis, there is a predominance of parakeratosis and acanthosis with minimal or no spongiosis and a dermal lymphocytic infiltrate.

If a skin biopsy taken in hand dermatitis, special stains for fungal elements should be performed to rule out a dermatophyte infection (ringworm).

Differential diagnosis eczema

The histopathologic features that characterize spongiosis also occur in a myriad of other skin disease they are not classically classified as 'eczema', which further confuses the definition. Examples of this include, but are not limited to pityriasis rosea, Gianotti Crosti syndrome, the cancel erythema, miliaria, Grover's disease, polymorphous light eruptions, papular urticaria, lichen striatus and some pigmented purples. The diagnosis of the particular type of spongiotic dermatitis depends on precise clinicopathologic correlations. For him pathologist To properly evaluate the biopsy, you must know the site and distribution of injuries, as well as the age of the patient. The clinic morphology of the lesions is also important: they are papules, vesicles, blisters, plates or patches? Are they pruritus? Are excoriations Present? How long have the lesions been present? Do they respond to conventional therapy?

In many cases, the pathologist can only make a diagnosis in the general category 'spongiotic dermatitis, not otherwise specified'. The pathologist should avoid diagnosing a eruption as spongiotic or eczema when the pathological changes actually represent a spongy simulator of eczema. For example, if the lesions are not pruritic, the pathologist must consider other diagnoses. If there is capillaritis, may suggest a pigment purple, in which case you should ask for an iron stain. A special stain for fungal forms (PAS or Grocott) should be ordered in most cases to exclude a dermatophyte infection. Localized acral eruptions in younger individuals should increase the possibility of Gianotti Crosti syndrome. If the clinical lesions are disseminated, itchy papulovesicles, the biopsy should be sectioned stepwise to look for diagnoses such as Grover's disease (which will show acantholysis) or papular urticaria (which will contain numerous interstitial eosinophils).

Most of the time, the histopathological examination does not allow a more explicit designation of the etiology or Pathogenesis. It is up to the pathologist to try to be as specific as possible and to the referring physician to provide the relevant clinical information.

Special studies for eczema

PAS staining should be done to rule out a fungal infection.