3 Pityriasis, nigra, piedra.pptx mycology

Superficial fungal infection, clinical microbiology, pityriasis versicolor, nigra , piedra

1. Pityriasis (tinea) versicolor It is caused by the yeast Malassezia furfur

2. Pityriasis versicolor It is a chronic mild superficial non-itchy mycosis of the stratum corneum of the skin. It is caused by a lipophilic yeast known as Malassezia furfur. The fungus is part of the normal microbial flora of the skin.

3. Pityriasis versicolor It grows usually sparsely in the seborrhoeic areas (scalp, face and chest) without causing disease. However, it is incriminated as a cause of scalp dandruff.

4. Pityriasis versicolor Pityriasis versicolor is more common in hot, humid climates and in people who sweat heavily, so it may recur each summer. In some individuals, for unknown reasons, it grows more actively on the skin surface. It is not transmitted from one person to an other because the yeast is a flora in human body.  

5. Pityriasis versicolor Clinical features: Pityriasis versicolor affects the trunk, neck, and arms. Other parts of the body are not affected. The lesions are discoloured,( hypo- or hyper-pigmented ) skin patches. They are usually not itchy.

6. Pityriasis versicolor Pale patches are more common in black people; this appearance is known as pityriasis versicolor alba, and is less likely to itch. Sometimes the patches start scaly and brown, and then resolve through a non-scaly and white stage.

7. Pityriasis versicolor

8. Pityriasis versicolor

9. Pityriasis versicolor

10. Diagnosis Diagnosis of pityriasis (tinea) versicolor includes evaluation of the clinical picture and laboratory investigations. Laboratory investigations:- 1) A yellow-green fluorescence can be observed on examination of the affected areas with Wood's light.

11. Diagnosis 2) Microscopic examination of a wet preparation of skin scraping (using KOH 10-20 % as a dekeratinizing agent) shows yeast cells. Culture technique is not appropriate for diagnosis of pityriasis versicolor because culture is often negative but still it can grow in Sabouraud’s medium.  

12. Treatment Topical and oral antifungal drugs are used to treat pityriasis versicolor. These include:- 1. Topical azoles including clotrimazole, miconazole, econazole and ketoconazole in various formulations. 2. Terbinafine gel.

13. Treatment Apply the drugs widely over the affected areas at least once a day for a minimum of two weeks. Patients with extensive or persistent pityriasis versicolor are given oral ketoconazole tablets or itraconazole capsules for a few days.

14. Recurrences Oral antifungal treatment can be prescribed for one to three days each month as a preventative measure in those who have frequent recurrences.  

15. Tinea nigra It is due to infection with a brown mould, known as Exophiala (Hortaea) werneckii . It affects the skin of the palm and or sole with persistent slowly growing brown or black patches. They are slightly scaly and do not itch. The disease is common in tropical regions and often affects those who sweat excessively. The mould usually inhabits the soil.

16. Tinea nigra

17. Tinea nigra

18. Tinea nigra

19. Tinea nigra Laboratory diagnosis:- Scrapings taken from the edge of the scaly lesion and addition of KOH 10-20 % will show hyphae under the microscope. The hyphae can be clear in colour, yellow or brown and are septate. Culture in Sabouraud’s medium results in growth of black colonies of Exophiala (Hortaea) wernekii within a week.

20. Tinea nigra Treatment Tinea nigra usually clears with topical antifungal drugs applied for 2 -4 weeks. Caution: It may be missed diagnosed as malignant melanoma ; otherwise, it has no serious health bearings.

21. Piedra P iedra is the fungal infection of the hair shaft leading to formation of firm nodules which are ascomycete fruiting body of the fungus, know as an ascostroma. Multiple colonization of the same hair strand is common.

22. Piedra The infection may affect hairs of the scalp, body and genital area. The source of infection is unknown, and even though person-to-person transmission has been suggested.

23. Piedra Clinical varieties of both types pf piedra are mostly asymptomatic. However, according to the severity of the infection, progressive weakness of the hair shaft occur causing hair breakage.

24. Piedra There are two type of piedra: 1. Black piedra: In this type the causative fungus is Piedraia hortai. There are brown to black nodules found firmly adherent to the hair shaft which can not be readily detached.

25. Black piedra The area most frequently involved is the scalp. A metallic sound may be heard when the hairs are combed.

26. Black piedra

27. Black piedra

28. White piedra In this type the hair nodules are white; it is due to Trichosporum beigelii . These nodules are loose aggregates of hyphae and arthroconidia. In white piedra, the nodules are easily detached from the hair shaft by rubbing along its length. The colour varies from white to light brown. Pubic hair, beard and mustache are the most commonly infected areas.

29. White piedra

30. White piedra

31. Treatment Treatment of piedra includes shaving of the affected hairs or topical application of salicylic acid, 2% formaldehyde or azole creams. Oral therapy with either ketoconazole or terbinafine is effective. However, relapse rates are high even after adequate therapy.