‘A Case of an Angry-looking Rash’
A woman of fifty-six years visited Dr Walter Larsen in the examination room in Portland Oregon on a Tuesday two days earlier. He was now convinced on inspecting the patient in person that the rash was no longer a case of poison oak.
Back then, the patient was concerned; now she was scared of what her clinical problem was. Her fair hands and arms were hidden vicious-looking streaks of red. Dr Larsen blurted that the case was no longer concerning poison oaks. I told you the patient replied almost instantly, her lowered down gown revealed the scarlet lines to criss-cross up her arms, across her neck, down her back, her chest and abdomen. Dr Larsen still had no clue as to what the strange looking rash might be, but it was certain that it got a whole lot uglier in just a couple of days.
The patient noticed the rash on a Monday and initially it was just confined to back of her hands and it did not really hurt or itch. As the rest of the same day went on, the rash would turn to become more red and angry looking. Overnight, tiny blisters would form over the red regions. On sight of her sister’s dilemmas, the patient’s sister urged her to see a doctor. The patient was reluctant at first, she was laid of from work at the local power company and had no health insurance. During her first visit with Dr Larsen, he suspected it to be some kind of allergic contact dermatitis, probably from a poison oak. She told him that she’d been outdoors but had not come across any poison oak. The doctor was hell-bent that it was a case of contact dermatitis due contact with poison oak. The patient did find the diagnosis apt enough. This rash was tender on touch but it was not itchy. The doctor administered a steroid cream lest she would visit in back in a couple of days.
His defence was that she was among plants and that rash closely resembled a poison oak enough to confuse a doctor. After two days, she was back at his examining office, the blisters on her hands had now been hardened and the red streaks were darker and much raised. The welts that had previously been previewed on her neck, legs back and abdomen made her appear flogged. The discomfort of her appearance had gone to the point of her masking it with the aid of gloves and long-sleeves.
A terror of a view don’t you think?
The red streaks started to look like she’d scratch herself vigorously as way to cope with her skin condition but she told her doctor that wasn’t the case. The rash was on the middle of her back where she would have not been able to reach. The doctor used his pen to just faintly draw down her back causing a line to form as the tip of his pen moved. As he watched her skin’s reaction to the tracing of the pen’s movement, he explained how some people have a condition called as dermographism. This occurs when the skin responds allergically on being touched. On applying pressure just as he did on to the skin of these patients would cause a red welt and as he waited for a while the mark faded. Dermographism is an exaggerated weal and flare response that occurs within minutes of the skin being stroked or scratched. Dermographism is the most common form of physical or chronic inducible urticaria. It is also called dermatographia and dermographic urticaria.
Had she started taking any new medications recently? She shook her head; it was a no. There was no fever, no symptoms other than the rash? None, she answered back to him. It was then that Dr Larsen decided to vanish from the room bringing in two of his younger colleagues, Dr Michael Adler had asked her on whether she had consumed any Shiitake mushrooms. “How did you know?” the patient asked. On Friday, she was offered a delicious Shiitake mushroom sample from the local grocery store that she enjoyed rather ravenously. The young doctor thanked her and the three of them walked out of the room. Dr Larsen finally informed her of the condition known as Shiitake dermatitis. It was first described in 1977. It had a much frequent occurrence in Asia but was rarely reported in the US. The rash is thought to be a toxic reaction to the starch-like component present in all Shiitake mushrooms. Its called lentinan, which breaks down on heat and so its only seen in raw or undercooked mushrooms.
Shiitake dermatitis is a distinctive rash that can occur following the ingestion of raw or undercooked shiitake mushrooms (Lentinula edodes). It is characterised by pruritic, erythematous, linear streaks that resemble whiplash marks, hence the name flagellate. Shiitake dermatitis is also known as flagellate erythema and toxicodermia.
“So, am I allergic to these mushrooms?!” the patient inquisitively asks. “Well, it’s not a true allergy, when someone is exposed to a bad substance and gets a bad response its only ever allergic when an immune response gets actively involved. When the rash is tested however there is a lack of an immune response, so it’s regarded as a toxic not allergic reaction. Shiitake flagellate dermatitis is a toxic reaction to lentinan, found in fresh, powdered, or lightly cooked shiitake mushrooms. Lentinan is a thermolabile polysaccharide that activates interleukin 1 secretion, leading to vasodilation, haemorrhage and rash. This hypothesis is supported by the observation that shiitake dermatitis is not seen with the ingestion of thoroughly cooked at a temperature > 145 C. Flagellate dermatitis does not result from cutaneous contact with the mushrooms.
Not everyone though gets this violent of a reaction from this hidden component. Those that don’t get this toxic reaction might be considered lucky as they could avail the benefits of what lentinan has to offer… Larsen orders a biopsy of the rash to ensure nothing was ever missed and he instructs that patient continue using the steroid creams, he recommends that she avoids uncooked shiitake mushrooms. Adler laughs admitting that it was sheer luck, he read a report of a patient developing a crazy-looking rash after eating shiitake mushrooms, the image relapsed his memories of the rash’s looks.
What’s so great about working in groups is that when you get stumped one of these guys will know the answer… It’s like doing a crossword puzzle with a friend.
The flagellate rash of shiitake dermatitis typically appears 24 hours after ingestion of raw or undercooked shiitake mushrooms.
- Onset can occur within a few hours and up to 5 days after ingestion of the mushrooms.
- Itchy erythematous papules and sometimes petechiae are arranged in linear streaks.
- There may be localised swelling.
- They most often affect the trunk, but may also affect limbs, neck and head. It does not affect mucosal surfaces.
- The rash can be worse on exposure to the sun.
- Associated gastrointestinal symptoms can occur.
The rash spontaneously resolves within a few weeks.
Systemic Symptoms
Some patients with shiitake flagellate dermatitis have other symptoms.
- Localised oedema
- Malaise
- Fever
- Lip tingling (has been reported 48 hours after eating)
- Discomfort when swallowing
- Diarrhoea
- Tingling of hands and feet
The diagnosis is clinical, based on the characteristic history of recent mushroom ingestion and on the appearance of the rash. There are no specific laboratory findings. Usual tests may include:
- Full blood count
- Urea and electrolytes
- Liver function tests.
Histopathology is nonspecific, demonstrating focal hyperkeratosis, spongiosis, dermal oedema and perivascular lymphocytic Infiltrate with eosinophils.
Shiitake flagellate dermatitis is a self-limiting condition. It is unknown if treatment speeds up the resolution of the rash.
- Oral antihistamines
- Topical corticosteroids
- Affected individuals should protect their skin from sun exposure while the rash is resolving.
There is generally improvement within 2 days and complete resolution after 3 weeks. Prevent future attacks by ensuring that Shiitake mushrooms are thoroughly cooked before eating.
Sources & Credit;
Diagnosis: Solving the Most Baffling Medical Mysteries-Lisa Sanders. (Cases go in no particular order!)
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