Lichen is a Latin word meaning ‘tree moss’, referring to the symbiosis of a fungus, usually of the class Ascomycetes, and algae, resulting in a composite organism that characteristically forms a crust-like or branching growth on rocks or tree trunks. But the term ‘lichen’ is also used for various skin diseases characterized by patchy eruptions of small, firm papules. But not all the diverse skin conditions illustrated are papular; biopsy may be required to confirm diagnosis.
For each of the twelve cases, study the image(s) and then answer the questions. You can click on the image to view a larger version if required.
Each case should take approximately 2 minutes to complete. There is a list of suggested further reading material at the end of the quiz.