Also known as: Yellow fungus disease
Yellow fungus disease is a serious, progressive fungal skin infection of lizards, especially bearded dragons, caused by Nannizziopsis (formerly Chrysosporium) species. The fungus invades the skin and can extend into deeper tissues and internal organs. It produces yellow to brown crusty, discolored, thickened, or ulcerated skin lesions that worsen over time and often recur. The disease is contagious between reptiles, frequently difficult to cure, and can be fatal in advanced cases.
Yellow fungus disease is an invasive fungal dermatitis caused by Nannizziopsis species (formerly grouped under Chrysosporium). It is best known in bearded dragons and is regarded as one of the more serious skin diseases of captive lizards because it does not stay superficial but can invade deeper tissues and organs.
The disease is caused by keratin-loving Nannizziopsis fungi, spread by direct contact between animals and through contaminated environments and equipment. Stress, immune suppression, poor husbandry, and skin injury all favor infection taking hold.
Signs are yellow, brown, or gray crusty patches, thickened or flaky skin, discoloration, ulceration, and abnormal or incomplete sheds. Lesions enlarge over time, can spread across the body, and may extend into underlying muscle and bone in advanced cases.
Diagnosis uses skin samples for fungal culture, cytology, and biopsy, along with molecular testing to specifically identify Nannizziopsis and distinguish it from other causes of skin disease such as bacterial dermatitis.
Treatment requires prolonged systemic antifungal medication, topical therapy, surgical debridement of affected skin, and supportive care, often continued over months. Relapses are common, the prognosis is guarded, and infected animals should be strictly isolated.
Prevent spread by quarantining and carefully inspecting all new lizards, maintaining strict hygiene with dedicated equipment, reducing stress and overcrowding, and disinfecting tools and surfaces between animals. Optimizing temperature, humidity, and nutrition keeps the skin healthy and more resistant to fungal invasion.
This content is for educational purposes and is not a substitute for professional veterinary advice. If you are worried about your pet, contact your veterinarian.
