Tinea versicolor

Tinea versicolor is a condition characterized by a skin eruption on the trunk and proximal extremities. The majority of tinea versicolor is caused by the fungus "Malassezia globosa", although "Malassezia furfur" is responsible for a small number of cases. These yeasts are normally found on the human skin and become troublesome only under certain circumstances, such as a warm and humid environment, although the exact conditions that cause initiation of the disease process are poorly understood.
The condition pityriasis versicolor was first identified in 1846. Versicolor comes from the Latin, from "" to turn + color. It is also commonly referred to as Peter Elam's disease in many parts of South Asia.
Signs and symptoms.
The symptoms of this condition include:
Pityriasis versicolor is more common in hot, humid climates or in those who sweat heavily, so it may recur each summer. 
The yeasts can often be seen under the microscope within the lesions and typically have a so-called "spaghetti and meatball appearance" as the round yeasts produce filaments.
In people with dark skin tones, pigmentary changes such as hypopigmentation (loss of color) are common, while in those with lighter skin color, hyperpigmentation (increase in skin color) is more common. These discolorations have led to the term "sun fungus".
Pathophysiology.
In cases of tinea versicolor caused by the fungus "Malassezia furfur", lightening of the skin occurs due to the fungus's production of azelaic acid, which has a slight bleaching effect.
Diagnosis.
Tinea versicolor may be diagnosed by a potassium hydroxide (KOH) preparation and lesions may fluoresce copper-orange when exposed to Wood's lamp. 
The differential diagnosis for tinea versicolor infection includes:
Treatment.
Treatments for tinea versicolor include:
Epidemiology.
This skin disease commonly affects adolescents and young adults, especially in warm and humid climates. The yeast is thought to feed on skin oils (lipids), as well as dead skin cells. Infections are more common in people who have seborrheic dermatitis, dandruff, and hyperhidrosis.