This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Erythmato-Squamous and Lichenoid Eruption, Subject name: Skin
[{'content': 'Pteryigum of nail is seen in - \nSelect and explain. \nA. Lichen planus, B. Psoriasis, C. Tineaunguium, D. Alopecia aerata', 'role': 'user'}, {'content': "Answer: A \nExplanation: Ans. is 'a' i.e., Lichen planusDorsal pterygiumo Winged appearance of nail due to a central fibrotic band divides a nail proximally in two.o Fibrotic band obstructs normal nail growth, eg lichen planusVentral pterygium or ptery gium inversum unguiso Occurs on the distal undersurface of the nail, with forward extension of the nail bed epithelium dislocating the hyponychium and obscuring the distal groove.eg:- trauma, systemic sclerosis, Raynaud's phenomenon, lupus erythematosus, familial and infective", 'role': 'assistant'}]