The patient was a 36-year-old woman who was 39 weeks pregnant. She was referred by the gynecology unit for treatment of a pruritic eruption that had appeared 3 days earlier. The patient had no relevant past history and was not taking any regular medication. Her pregnancy was progressing normally. She was in the habit of taking walks in a rural area, always with her trunk covered. She had eaten at an Asian restaurant with her partner, who had no skin lesions, 2 days prior to the onset of symptoms.

Physical examination revealed multiple linear, erythematous, pseudovesicular plaques (Fig. 1) on the patient's trunk, limbs, and face (Figs. 2 and 3). The lesions were not evanescent or scaly, and they spared the periumbilical region. No abdominal striae were visible.

Fig. 1.

.

(0.09MB).

Fig. 2

(0.05MB).

Fig. 3

(0.1MB).

Because of our initial clinical suspicion, we did not perform a skin biopsy or request any other tests.

What Is Your Diagnosis?

Shiitake dermatitis.

Symptomatic treatment with topical corticosteroids and oral antihistamines was initiated. New lesions continued to appear for 48hours. The condition then gradually improved and resolved completely within 2 weeks, leaving transient residual hyperpigmentation.

The shiitake mushroom (Lentinus edodes) is very common in Chinese and Japanese cuisine. Shiitake dermatitis has been known in Asian countries for many years1 and is becoming better known in the West as consumption of shiitake mushrooms becomes more widespread.2,3 This form of dermatitis is highly distinctive, with highly pruritic, erythematous papules and plaques scattered across the skin in a linear or flagellate pattern. The lesions are found primarily on the trunk and limbs and may also affect the face and neck. The eruption appears 24–48hours after ingestion of raw or undercooked shiitake mushrooms and resolves within a week.4 The diagnosis is usually made on a clinical basis because histology of the lesions shows nonspecific spongiotic dermatitis.1 Patch tests and prick tests are usually negative.1,4 Shiitake dermatitis is a toxic reaction caused by thermolabile polysaccharides such as lentinan that are found in shiitake mushrooms.1 The main condition that should be considered in the differential diagnosis is flagellate erythema associated with dermatomyositis5 or caused by bleomycin treatment. Allergic conditions such as conjunctivitis, rhinitis, asthma, and contact dermatitis have also been reported in shiitake mushroom growers.6

Shiitake dermatitis is treated symptomatically. The condition does not recur so long as the patient avoids eating shiitake mushrooms that are not fully cooked.

We present the case of this unusual mushroom-induced toxic eruption because the increasing prevalence of shiitake mushroom consumption could lead to new cases in Western countries. This case is of additional interest because it occurred in a pregnant woman.

The authors declare that they have no conflicts of interest.