Entoloma sinuatum is a poisonous mushroom found across Europe and North America. Some guidebooks refer to it by its older scientific names of Entoloma lividum or Rhodophyllus sinuatus. Entoloma is a genus of pink-spored fungi, of which this species is the largest. Occurring in parks or deciduous woodlands in late summer and autumn, it has an ivory to light grey-brown cap up to 20 cm (8 in) across, with a whitish stem and pink free gills.

It may be mistaken for the edible St Georges' mushroom (Calocybe gambosa), or miller (Clitopilus prunulus) and has been responsible for many cases of mushroom poisoning in Europe. E. sinuatum causes primarily gastrointestinal problems that, though not generally life-threatening, have been described as highly unpleasant. It is generally not considered to be lethal, although one source has reported deaths from the consumption of this mushroom.

Taxonomy

This species has a complicated taxonomic history, initially having been described as Agaricus lividus by French naturalist Jean Baptiste Bulliard in 1788, illustrated, although without an accompanying description. Christian Persoon later named it Agaricus sinuatus in 1801. German mycologist Paul Kummer gave it its current binomial name in 1871, antedating Lucien Quélet's Entoloma lividum by one year. It was listed as E. lividum in most books for many years, but it later became apparent that Bulliard's original illustration was of Pluteus cervinus.

Entoloma sinuatum has been the most widely accepted scientific name since 1955, and was promoted as such by Michael Noordeloos in his recent work on the genus. Initially Noordeloos had erected the new name Entoloma eulividum for the common form of the species (as E. lividum was invalid) after separating the older description of E. sinuatum as it described a form lacking yellow colour on the gills, so for a time in the 1980s there were two accepted species - the widespread E. eulividum with yellow-tinged gills and now-restricted and rare E. sinuatum. However he later felt these were merely colour variations and so this is the name universally recognised. A proposal was later made to conserve Entoloma lividum in 1999, citing its previous widespread use and Quélet's detailed description. However it was rejected in 2001 because Bulliard's original name was invalid.

To complicate matters further, Quélet had proposed a broader genus Rhodophyllus for all pink-gilled fungi with adnate or sinuate gills and angular spores in 1886, countering Kummer's erection of Entoloma to genus level. These two classifications coexisted for many decades, with mycologists and guidebooks following either author, and the alternate scientific name Rhodophyllus sinuatus was commonly seen. However, later authorities have tended to favour Entoloma.

Thus, the current most widely accepted name is Entoloma sinuatum, the specific epithet sinuatum being derived from the Latin for wavy, referring to the shape of the cap, while the generic name is derived from the Ancient Greek words entos/ἐντός 'inner' and lóma/λῶμα 'fringe' or 'hem' from the inrolled margin. The specific epithet lividum was derived from the Latin word lividus meaning 'lead-coloured'. The various common names include livid entoloma, livid agaric, livid pinkgill, leaden entoloma, and lead poisoner. In the Dijon region of France it was known as le grand empoisonneur de la Côte d'Or ("the great poisoner of Côte d'Or"). Quélet himself, who was poisoned by the fungus, called it the millers purge, akin to another common name of false miller.

Description

Entoloma sinuatum has a large and imposing epigeous (aboveground) fruiting body (basidiocarp), bearing a cap 6–15 cm (2½–6 in) wide, though diameters of 25 cm (10 in) have been recorded. It is convex to flat, often with a blunt boss in its center and wavy margins, ivory white to light grey-brown in colour, and darkening with age. The distant gills are free, generally (but not always) yellowish white before darkening to pink and then red. When looked at from underneath, a characteristic groove can be seen in the gill pattern circumnavigating the stalk.

The spore print is reddish brown, with angular spores 8–11 x 7–9.5 μm, roughly six-sided and globular in shape. The stout white stipe is generally 6–10 cm (2½–4 in) high and lacks a ring. It may be bulbous at the base. The taste is mild, although it may be unpleasant. The mushroom's strong and unusual odour can be hard to describe; it may smell of flour, though is often unpleasant and rancid.

The form lacking yellow colour on the gills is rare but widespread, and has been recorded from Austria, France and Holland.

Confusion with the highly-regarded miller or sweetbread mushroom (Clitopilus prunulus) is a common cause of poisoning in France; the latter fungus has a greyish-white downy cap and whitish decurrent gills which turn pink with maturity. Entoloma sinuatum can also be confused with St Georges' mushroom (Calocybe gambosa), though the gills of the latter are crowded and cream in colour, and the clouded agaric (Clitocybe nebularis), which has whitish decurrent gills and an unusual odour. The rare and edible all white dovelike tricholoma (Tricholoma columbetta) has a satiny cap and stem and a faint, not mealy, odour. It may be confused with Clitocybe multiceps in the Pacific Northwest of North America, though the latter has white spores. A casual observer may mistake it for a field mushroom (Agaricus campestris).

Distribution and habitat

Entoloma sinuatum is fairly common and widespread across North America as far south as Arizona. It also occurs throughout Europe through to the British Isles including Ireland, though it is more common in southern and central parts of Europe than the northwest. Eastwards, it has been recorded in the Black Sea region of Turkey.

Entoloma sinuatum has been found in fairy rings. Fruiting bodies are found in deciduous woodlands in late summer and autumn under oak, beech, and less commonly birch, often on clay soils, though they may also occur in parks. Most members of the genus are saprotrophic, though this species has been recorded as forming an ectomycorrhizal relationship with the willow (Salix).

Toxicity

This fungus has been cited as being responsible for 10% of all mushroom poisonings in Europe. In Geneva alone, 70 people required hospital treatment in 1983. Poisoning is said to be mainly gastrointestinal in nature, symptoms of diarrhoea, vomiting and headache occur 30 min to 2 hours after consumption and last for up to 48 hours. Acute liver toxicity and psychiatric symptoms like mood disturbance or delirium may occur. Rarely symptoms of depression may last for months. At least one source reports there have been fatalities in adults and children.

Hospital treatment of poisoning by this mushroom is usually supportive; antispasmodic medicines may lessen colicky abdominal cramps and activated charcoal may be administered early on to bind residual toxin. Intravenous fluids may be required if dehydration has been extensive, especially with children and the elderly. Metoclopramide may be used in cases of recurrent vomiting once gastric contents are emptied.

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