Light micrograph of a cleistothecia, which is a structure containing reproductive spores, of a fungus (Arthroderma sp.). Inside this structure spores are grouped in small clusters known as asci. Arthroderma is a genus of dermatophyte fungi, which are fungi that grow on skin, hair and nails causing dermatophytosis (ringworm and tinea). These are infections that cause raised, red skin lesions and can lead to hair loss. Treatment is usually straightforward, requiring the topical application of antifungal medication for 1-2 weeks.