impaginato piccolo - Società Italiana di Parassitologia (SoIPa)

Parassitologia 50: 69-71, 2008
Skin diseases associated with Malassezia species in humans.
Clinical features and diagnostic criteria
E.M. Difonzo 1, E. Faggi 2
1 Dipartimento di Scienze Dermatologiche, Università di Firenze; 2 Dipartimento di Sanità Pubblica, Università di Firenze
Abstract. Malassezia yeasts not only cause the well known pityriasis versicolor and folliculitis, but also play
an important role in other skin diseases, including seborrheic dermatitis and atopic dermatitis.
The presence of Malassezia yeasts may be confirmed by direct microscopic examination and cultures of
skin scrapings.
In pityriasis versicolor the direct microscopic examination is the rapidest and surest test for confirming the
clinical diagnosis. The preparation will show a cluster of globose budding spores with thick or double wall
and short hyphae. For detecting Malassezia in the other diseases the cultures is preferable.
Culture is useful both for confirming the clinical diagnosis and for epidemiological investigations. The identification
of the Malassezia species is not easy. The microscopic observation of the colony direct towards
the identification of Malassezia species, but it is not enough to identify the colonies definitely. Several biochemical
tests are necessary for a precise identification, such as catalase reaction, growth on media without
lipid sources, ability to utilize hydrophilic emulsifiers as sole lipid source, esculin test, tryptophan test.
Key words: Malassezia species, pityriasis versicolor, seborrheic dermatitis, biochemical tests.
The yeasts of the genus Malassezia are normal skin
commensals and lie in the stratum corneum and acroinfundibulum
of the sebaceous follicle, particularly in
sebaceous –rich areas, as face, scalp , head and upper
back (Faergemann J, 1983; Faggi E, 1994).
Malassezia not only causes the well known pityriasis
versicolor and folliculitis, but also play an important
role in other skin diseases, including seborrheic dermatitis
and atopic dermatitis (Gupta AK, 2004; Aspres
N, 2004; Sugita T, 2003).
Pityriasis versicolor (PV)
PV is a worldwide chronic or relapsing mycosis, predominant
in young adults and localized on the upper
trunk, chest, back and shoulders. The disease is characterized
by round or oval, hypo-or hyperpigmented macules
covered with thin scales, which are easily removable.
Margins of the lesions are sharply delineated.
Lesions are 1 to 5 mm in diameter in the beginning, but
may coalesce to form variously shaped patches. Their
color is variable from whitish to pink, salmon or brown
according to several factors, such as the age of the
lesions, inflammatory response of the host, exposure to
sunlight, as well as normal pigmentation of the patient.
The conditions allow the overgrowth of Malasssezia in
certain people and cause PV are not clearly defined.
Numerous factors seem to favour the change from a
yeast form to an invasive hyphal one. Important factors
are hyperhidrosis , occlusive clothing, and genetic predisposition.
Correspondence: Elisa M. Difonzo
Dipartimento di Scienze Dermatologiche, via della Pergola 64,
50121 Firenze, Italy
Tel: +39 055 27588935; fax: +39 055 2758381;
e-mail: elisa.difonzo@asf.toscana.it
Malassezia spp cultured from lesions of PV are
Malassezia globosa and Malassezia sympodialis
(Gupta AK, 2004; Gupta AK, 2001; Gaitanis G, 2006;
Tarazooie B, 2004; Hernandez F, 2003; Crespo-Erchiga
V, 2006; Morishita N, 2006).
Malassezia folliculitis (MF)
MF is a chronic disease characterized by small erythematous
follicular papules and/or pustules localized on
upper trunk. Patients develop moderate or even severe
pruritus. The lesions heal with an easily removable
crust. Most frequently MF affects young oil skinned
people with acne vulgaris or seborrheic dermatitis.
The development of MF is favoured by hot and humid
climates, use of antibiotics, above all tetracyclines.
Histological findings show invasion of the central and
deep follicle with large number of Malassezia yeasts
and inflammatory infiltrate consisting of lymphocytes
and histiocytes, along with focal rupture of the follicular
wall.
Seborrheic dermatitis (SD)
DS is a common chronic inflammatory disorder localized
in sebaceous-rich areas occurring in 3% to 5% of
the general population. The incidence is much higher in
patients who are immunocompromised, especially
those with AIDS, ranging from 30% to 80%. The disease,
which is more common in male patients, tends to
occur most frequently in adolescents and young adults.
The characteristic presentation shows erythematous
patches covered by greasy scales. Pityriasis simplex
capitis ( so-called “dandruff”) is a mild form of scalp
SD. On the face the disease affects forehead, eyebrows,
glabella, and nasolabial folds. On the sternal and interscapular
regions DS is characterized by figurated circi-