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''Neoscytalidium dimidiatum'' was first described in 1933 as ''Hendersonula toruloidea'' from diseased orchard trees in
Egypt Egypt ( , ), officially the Arab Republic of Egypt, is a country spanning the Northeast Africa, northeast corner of Africa and Western Asia, southwest corner of Asia via the Sinai Peninsula. It is bordered by the Mediterranean Sea to northe ...
. Decades later, it was determined to be a causative agent of human
dermatomycosis A dermatomycosis is a skin disease caused by a fungus. Most dermatomycoses are mild and resolve without treatment, but many are treated clinically with topical antifungal medicines. Oral antifungals are also an option for treatment. One of the m ...
-like infections and foot infections predominantly in tropical areas; however the fungus is considered to be widespread. A newer name, ''Scytalidium dimidiatum'', was applied to a synanamorph of ''Nattrassia mangiferae'', otherwise known as ''Neofusicoccum mangiferae''. Substantial confusion has arisen in the literature on this fungus resulting from the use of multiple different names including ''Torula dimidiata'', ''Fusicoccum dimidiatum'', ''Scytalidium dimidiatum'', and ''Hendersonula toruloidea''. Additionally, ''Scytalidium lignicola'' and ''Scytalidium lignicolum'' are often considered earlier names of ''N. dimidiatum''.Onychomycosis caused by Scytalidium dimidiatum. Report of two cases. Review of the taxonomy of the synanamorph and anamorph forms of this coelomycete
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History and taxonomy

In 1933, British mycologist Dr. Rolland Marshall Nattrass described an arthroconidial asexual fungus that he named ''H. toruloidea'' that was responsible for causing die-back disease of plum, apricot and apple trees in Egypt. At the time, he recognized that single spore cultures of the fungus yielded two "forms" in culture – a mycelial form resembling members of the genus ''Torula'' that produced fragmenting chains of arthroconidia, and a pycnidial form characterized by the production of greenish, ellipsoidal spores that oozed from tiny sacs. The name ''H. toruloidea'' applied to the latter pycnidial form. Others likened the ''Torula'' form to ''Torula dimidiata'' described by Otto Penzig in 1882. Despite that the fungus was known by this name for over 50 years by one or the other of these names, increased scrutiny of the species and its close relatives using molecular genetic methods spawned significant controversy in its taxonomy and naming. In 1989 Sutton and Dyko created the genus ''Nattrassia'' to accommodate ''H. toruloidea'' and applied the name ''Scytalidium dimidiatum'' to the
mycelial Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fou ...
synanamorph. They also included in the new genus ''Nattrassia'' a fungus described by father-son mycologists
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and Hans Sydow as ''Dothiorella mangiferae'', which became ''Nattrassia mangiferae'', thought to be very closely related to and perhaps indistinguishable from Nattrass's original pycnidial form. Farr and coworkers recognized that both states were asexual forms affiliated with the genus ''Fusicoccum'', an anamorph of the plant pathogenic ascomycete genus, ''Botryosphaeria''. They proposed the transfer of ''Scytalidium dimidiatum'' to the genus ''Fusicoccum'' as ''F. dimidiatum''. A reappraisal of the family Botryosphaeriaceae by Crous and coworkers in 2006 concluded that the genus ''Fusicoccum'' was
polyphyletic A polyphyletic group is an assemblage that includes organisms with mixed evolutionary origin but does not include their most recent common ancestor. The term is often applied to groups that share similar features known as Homoplasy, homoplasies ...
, and they created a new genus, ''Neoscytalidium'' to accommodate Nattrass's fungus. Separately they erected the genus ''Neofusicoccum'' to accommodate ''Nattrassia mangiferae''. Crous and colleagues concluded it inappropriate to collapse the entirety of ''Scytalidium'' with ''Fusicoccum'' because they demonstrated ''N. dimidiatum'' to be phylogenetically distinct from ''Neofusicoccum mangiferae''; thus, they interpreted ''N. dimidiatum'' to be the correct name for Nattrass's fungus.


Growth and morphology

This filamentous fungus produces sinuous and irregular
hyphae A hypha (; ) is a long, branching, filamentous structure of a fungus, oomycete, or actinobacterium. In most fungi, hyphae are the main mode of vegetative growth, and are collectively called a mycelium. Structure A hypha consists of one o ...
and is characterized by rapidly growing colonies that are deeply tufted with dense, darkly coloured, ropy aerial
mycelium Mycelium (: mycelia) is a root-like structure of a fungus consisting of a mass of branching, thread-like hyphae. Its normal form is that of branched, slender, entangled, anastomosing, hyaline threads. Fungal colonies composed of mycelium are fo ...
. Cultures are rapidly growing, initially light in colour and becoming dark brown and then black with age. Both arthroconidia and pycnidia may be produced in the same culture. Cultures of the fungus derived from human skin tend to be black in colouration.


Habitat and ecology

''Neoscytalidium dimidiatum'' is mainly found in tropical to subtropical environments, such as in South America, Southeast Asia, India and Africa. In addition to these regions, this fungus is endemic to parts of west and central Africa, the Caribbean and Asian, but more cases are being seen in temperate countries, possibly as a consequence of immigration from tropical regions. The fungus occurs in nature in soil and on decaying wood.


Human infection

''Neoscytalidium dimidiatum'' has been described as an agent to cause infections referred to as dermatomycosis,
onychomycosis Onychomycosis, also known as tinea unguium, is a fungal infection of the nail. Symptoms may include white or yellow nail discoloration, thickening of the nail, and separation of the nail from the nail bed. Fingernails may be affected, but it is ...
,
ringworm Dermatophytosis, also known as tinea and ringworm, is a mycosis, fungal infection of the skin (a dermatomycosis), that may affect skin, hair, and nails. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the a ...
or
tinea Dermatophytosis, also known as tinea and ringworm, is a fungal infection of the skin (a dermatomycosis), that may affect skin, hair, and nails. Typically it results in a red, itchy, scaly, circular rash. Hair loss may occur in the area affe ...
, affecting human nails, toe webs and feet, and skin, forming hyphomycete, and also sometimes infecting the palms of hands but this is a rare occurrence. To cause these infections in humans, infections occurs through contact with contaminated soil or plant materials, or nail or skin tissue from an infected person, causing superficial skin infections similar to dermatophytosis called Scytalidiosis. Although established to cause dermatomycosis and onychomycosis, invasive infection by ''N. dimidiatum'' is rare, resulting in limited case reports and limited information available for clinical progression and treatment. as well as there is no currently know oral or
topical A topical medication is a medication that is applied to a particular place on or in the body. Most often topical medication means application to body surfaces such as the skin or mucous membranes to treat ailments via a large range of classes ...
treatment for infection with this fungus. These result in the invasion of tissue and organs causing systemic diseases. Infection can occur in both immunocompetent and immunosuppressed patients, but deep infections occur mainly in immunosuppressed/ immunocompromised individuals with a 50% case mortality.
Melanin Melanin (; ) is a family of biomolecules organized as oligomers or polymers, which among other functions provide the pigments of many organisms. Melanin pigments are produced in a specialized group of cells known as melanocytes. There are ...
is characteristically produced by the fungus in vivo in diseased human tissue where its presence has been interpreted as an important pathogenic factor. Although limited in case reports, there have been some reported cases of ''N. dimidiatum'' causing dermatomycosis or onychomycosis in places such as
Jamaica Jamaica is an island country in the Caribbean Sea and the West Indies. At , it is the third-largest island—after Cuba and Hispaniola—of the Greater Antilles and the Caribbean. Jamaica lies about south of Cuba, west of Hispaniola (the is ...
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,
Algeria Algeria, officially the People's Democratic Republic of Algeria, is a country in the Maghreb region of North Africa. It is bordered to Algeria–Tunisia border, the northeast by Tunisia; to Algeria–Libya border, the east by Libya; to Alger ...
,
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, the United States and the United Kingdom. In addition, there have been some papers reporting infections besides dermatomycosis and onychomycosis, such as discovery of this fungus confirmed by DNA analysis to cause a fatal case of lung disease. Similarly, a case of lung infection has been reported in a
dolphin A dolphin is an aquatic mammal in the cetacean clade Odontoceti (toothed whale). Dolphins belong to the families Delphinidae (the oceanic dolphins), Platanistidae (the Indian river dolphins), Iniidae (the New World river dolphins), Pontopori ...
. A case of rhinosinusitis, a disease where it is believed that fungi play a role in the disease process, was reported to have been caused by ''N. dimidiatum''.


Plant disease

''Neoscytalidium dimidiatum'' has been mainly described as an opportunistic plant pathogen, causing pit canker and spot on the stem of plants or fruits, as well as internal black rot of fruits, but a case of internal brown rot of pitahaya was reported from China. Similarly in Malaysia was a report of the fungus causing stem canker of red-fleshed dragon fruit, and a similar report of stem canker on grapevine in California.


References

{{Taxonbar, from=Q6992872 Botryosphaeriaceae Fungi described in 1882 Fungus species