Spongiotic Reaction Pattern

SPONGIOSIS

With Epidermal eosinophils Consider Allergic contact dermatitis (Langerhans cell microabscsses, no necrotic keratinocytes) Photoallergic dermatitis (necrotic keratinocytes) Incontinentia pigmenti (newborn female)

With Epidermal Neutrophils Irritant contact (no necrotic keratinocytes) Phototoxic dermatitis (necrotic keratinocytes) Tinea (Parakeratosis and sandwich sign . Some guttate psoriasis (spongiosis and subcorneal neutrophils)

 

Spongiosis is the accumulation of fluid between the keratinocytes in the epidermis causing the desmosomes to stretch.  This is most obvious in the prickle layer of the skin in the stratum spinosum.  If the amount of fluid between the keratinocytes increases then sometimes intraepidermal vesicles can be seen. 

The next thing that you should look for if you spot spongiosis is to see if there are any cells infiltrating the epidermis and are these cells neutrophils, lymphocytes or eosinophils.  If they are neutrophils then look to see where they are accumulating.  If they are accumulating in the stratum corneum then consider that the patient has early psoriasis which may well have a little bit of spongiosis.  Look to see though if they have any evidence of fungal hyphae in the stratum corneum because it may be that this is a dermatophyte infection and also look to see if there is any bacteria with signs of secondary infection of eczema, particularly staphylococci. 

If instead the cells are eosinophils, then consider the potential causes of eosinophilic spongiosis.  These include a spongiotic drug reaction, particularly with the thiazide diuretics but also conditions such as pemphigus or pemphigus  vegetans.  Now as well as having spongiosis in these conditions you also should have acantholysis, in other words separation of the keratinocytes.  Bullous pemphigoid can also give some eosinophilic spongiosis early on as can allergic contact dermatitis and even arthropod bites.  A rare type of eosinophilic spongiosis can occur in Ofugi's disease where the eosinophils are associated with follicles, particularly in the infundibulum.  There is also the rare inherited disorder of Incontinentia pigmenti particularly the very first stage where there can be spongiosis with intra epidermal vesicles which are packed with eosinophils.  There is usually some evidence of dyskeratotic cells as well in Incontinentia pigmenti.

Neutrophilic spongiosis we have talked about as being a feature of psoriasis and also of dermatophyte infections and possibly secondary bacterial infection, but it may also be part of an acute generalised eczematous pustulosis or AGEP which is usually a drug reaction to drugs such as Tegretol or some of the sulphonamide antibiotics.  Rarely IgA pemphigus can also give rise to neutrophils high in the epidermis under the stratum corneum, but most cases of pemphigus will show you an eosinophilic infiltrate with eosinophilic spongiosis.

If you primarily see lymphocytes and spongiosis, look at the lymphocytes and see if they are atypical.  If they are atypical and especially if they are small congregations of them then these may be Pautrier microabscesses and they are a feature of early T-cell lymphoma of the skin.  This can be a difficult diagnosis to make early on.  One of the variants of T-cell lymphoma is what is called small plaque parapsoriasis and in this condition there may be mainly a spongiotic pattern with mild individual atypical lymphocytes in the adjacent epidermis.  This is usually reported as chronic superficial dermatitis, but over time the lymphocytes congregate into small Pautrier microabscesses and become more atypical and the areas of skin will thicken and look more like the plaque stage of T-cell lymphoma.

I think it is always important to remember the mnemonic for the clinical diseases that are associated with these red scaly disorders and that is the PMs PET with his little cat called PETAL.  PET is for psoriasis eczema tinea, the A for annulare erythema and the L for lupus or perhaps early lichen planus.  The initial P is for pit rosea, pityriasis versicolor, pityriasis rubra pilaris and the M is for mycosis fungoides, the S is for solar damage, syndromes and perhaps scabies.  These will all give rise to red scaly disorders.

Certainly eczema is the most common cause of spongiosis but we have already said that spongiosis can be seen in some early forms of psoriasis and it also can be seen in pityriasis rosea and in dermatophyte infections.  The A stands for annulare erythema and erythema annulare centrifugum is the commonest of the annulare erythemas.  The primary feature you notice histologically is usually a superficial and deep perivascular lymphocytic infiltrate, but many cases will show a degree of spongiosis as well.  Those that do will clinically have scale whereas there are forms of erythema annulare centrifugum without any scale and these won't show the same degree of spongiosis.

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Atopic dermatitis is obviously one of the commonest dermatitic disorders that we will see that shows some degree of spongiosis.  The more acute and weeping the condition is clinically the more likely the spongiosis is going to be significant and it is when small accumulations of the spongiotic fluid break out on the surface of the skin that you have the small erosions that are so typical of the dermatitic process.  Drier forms and the more chronic lichenified forms of dermatitis though won't show the same degree of spongiosis, but will show epidermal acanthosis and some hyperkeratosis.  In contrast acute contact dermatitis can show marked spongiosis and often  intraepidermal vesiculation.  This is particularly likely with a plant contact dermatitis.

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Seborrhoeic dermatitis will also show a degree of spongiosis but it is centred around some hair follicles and these also show the phenomenon of parakeratosis with parakeratosis around the ostial openings.  There may be overlying crust that has neutrophils in it, but again the crust is centred around follicles.  This is reflected in the greasy clinical appearance of seborrhoeic dermatitis.

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Pompholyx eczema also gives rise to prominent vesicles in the epidermis but this is because of the overlying fixed stratum corneum not allowing the fluid to escape easily.  Pompholyx eczema is particularly seen on the sides of the fingers and toes.

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Stasis dermatitis is mainly seen in the elderly with an impaired venous or lymphatic circulation and it is most prominent around the medial malleolus.  As well as having mild spongiosis the major thing you are going to see is proliferation of superficial dermal blood vessels.  In cases where there is persistent and significant venous hypertension you will get capillaritis with extravasation of red blood cells and this gives rise to the brown hemosiderin pigmentation particularly seen in these areas.  There is often also a degree of fibrosis.  Rarely if this condition persists you may get underlying panniculitis as well and features described as lipodermasclerosis.

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Spongiotic drug reactions are characterised by varying degrees of spongiosis, sometimes with intraepidermal vesicles occurring.  Usually the cells that infiltrate are eosinophils but plasma cells can also be seen in some cases.  The reaction most likely to give intraepidermal vesicles is in fact an allergic contact dermatitis, but as I have already said drugs such as thiazide diuretics and calcium channel blockers can also cause spongiotic drug reactions.  The eosinophils may infiltrate into the epidermis or they may be mainly perivascular in the dermis.

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 The Gianotti-Crosti syndrome is usually diagnosed on the basis of papules or papulo vesicular lesions on the outer aspects of the arms, legs and the cheeks in a child who is otherwise well.  If these are ever biopsied then the lesions may show mixed pathologies with focal areas of spongiosis, some oedema in the dermal papillae and quite marked perivascular lymphocytes.  There is a degree of overlying parakeratosis but many times these lesions don't seem scaly.

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Grover's disease is another condition that can cause spongiosis but then Grover's can cause a variety of histologies.  Often it is recommended that you take several biopsies to show this variability in histological reaction patterns.  Spongiosis is perhaps the commonest pattern but acantholysis is the one that is usually needed to make a definitive diagnosis. The combinations of focal acantholysis and spongiosis are highly suggestive of Grover's disease.  Many cases of Grover's have an associated dermatitis in the surrounding skin.

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The PUPPPS syndrome or pruritic urticarial papules and plaques of pregnancy again is a diagnosis that is usually made clinically.  It is usually red and in most cases it is not scaly.  The lesions occur in the stretch marks.  Histologically there is a degree of spongiosis but it is often relatively mild.  There is more likely to be oedema of the papillary dermis with a superficial perivascular lymphocytic infiltrate.  Again often the clinical history is needed to give the histological diagnosis.

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Pityriasis alba is one of the mild variants of atopic dermatitis so you would expect any degree of spongiosis is going to be quite mild.  There may be a reduction of melanin in the basal layer as well that accounts for the white spots that are seen in this condition. 

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Other unusual conditions that can occur in children with spongiosis include lichen striatus but as the name suggests there is usually a mixture of both lichenoid histology and spongiotic reaction patterns.  The fact that there is significant lichenoid infiltrate means that there is usually basal layer damage and melanocytic damage so there are often melanophages in the dermis. Because of the lichenoid nature of the T-cell infiltrate there are usually some dyskeratotic cells where there has been a degree of satellite cell necrosis.  The lymphocytic infiltrate in the skin also extends around eccrine glands and this can be a useful feature in making the diagnosis.

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We have spoken already about lymphocytic infiltrates in mycosis fungoides and that the lymphocytes are usually atypical and may congregate in Pautrier microabscesses.  In very early cases it can be difficult to make this diagnosis and the lesions may be reported as chronic superficial dermatitis so you have this mild spongiosis with associated atypical lymphocytes infiltrating the epidermis.  

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