Abstract
Case history
A 55-year-old patient presented to his GP with widespread groups of symmetrical popular, pompholyx-like eruptions on arms, back (Fig. 1) and both legs (Fig. 2) appearing over a few weeks. The lesions were very itchy and those on the legs were rounded and crusty (Fig. 1). The rash was getting worse and stopped him from sleeping. He was suffering from joint pains affecting hands and feet. He was under the care of a rheumatologist for inflammatory arthritis (positive cyclic citrullinated peptide of 7.4), but not on any specific treatment for this. He has a history of hypertension, alcoholic liver disease (but has stopped drinking excessively) and depression. He takes paroxetine, glucosamine and ibuprofen.
Multiple small rough leathery eczematous patches on lower back. Crusted scaly eczematous patch on right lower leg.
The intensely itchy, sore rash and joint pains were affecting his manual job, which requires a lot of heavy lifting and handling of boxes. The patient initially presented to the pharmacist who gave him a combination of topical steroid and anti-fungal cream. He used the creams but these had no effect on the rash. His friend asked him to see his GP thinking the rash might be psoriasis related to the joint pain.
He was seen in the surgery, and given a topical and very potent steroid (Dermovate™). This had no effect after 2 weeks. His GP referred for a dermatology opinion and subsequently the diagnosis of disseminated dermatitis with interface reaction was made. The patient was started on 30 mg oral steroid for 5 days, reducing the dose by 5 mg every 5 days. In addition to this, the dermatologist suggested very potent topical steroid ointment (not cream) for 2 weeks and then a change to a lower potency topical steroid ointment for another 2 weeks.
Topical steroids are better applied after a quick shower in a ‘soak and seal’ approach to get better control. The use of topical steroids should be encouraged in a steroid ladder fashion, stepping down and up as self-directed by the patient according to the severity of the rash. The patient had a very good response to the oral steroid. The dermatologist also suggested the use of a soap substitute and a good moisturiser.
Discussion
Interface dermatitis (Id reaction) or autoeczematisation, is a disseminated reaction of the skin at a place distant to a primary cutaneous infection or stimulus. The exact cause of id reactions is unknown. One of the factors is the release of T lymphocytes after days or weeks of exposure to a stimulus (antigens). The stimulus can be infections (such as viruses, bacteria or parasites), contact dermatitis, stasis dermatitis and immunisation reactions.
The exact prevalence of Id reactions is unknown. One study showed that 17% of patients with dermatophyte infections developed an id reaction (Bertoli et al., 2021). Id reactions have been reported in up to 37% of patients with stasis dermatitis (Bertoli et al., 2021).
Id reactions present as widespread, symmetrical eruptions of papules with a kerion, usually associated with inflammatory tinea pedis. They are intensely pruritic and involve forearms, thighs, legs, trunk, face, hands, neck and feet (in descending order of frequency). Laboratory workup of Id reactions is indicated for the dermatophytids. Strict criteria include a proven dermatophyte infection.
The aim of management is to treat the underlying infection or dermatitis, which should lead to prompt resolution, reduce morbidity and prevent complications. Recurrence is common. Systemic and topical corticosteroids help lesion resolution and provide symptomatic relief of pruritis. The strength and administration of topical corticosteroid choice is based on the extent, location and severity of the eruptions. Antihistamines relieve pruritis.
In summary, disseminated eczema is an acute generalised dermatitis that occurs in response to a localised inflammatory skin disease. This is also called an id reaction or autoeczematisation. The cause is often unknown, but it may be owing to an autoimmune reaction. Taking a careful history of the initial site of infection may help determine the cause of the disease. Id reaction is often underdiagnosed. The diagnostic tool may involve skin culture for infections. The treatment is with a combination of antihistamine, oral and topical steroids. The prognosis is excellent with appropriate treatment.
