Hello and welcome to HCM,
A red rash on the penis spreading to the thigh can occur in number of disease processes.
There are many skin diseases charaterised by red rashes like
fungal infection,
psoriasis, erthema, eczema,
erythroderma to name a few.
Are the lesions associated with itch, discharge, or any swelling in the inguinal region (lymph node enlargement).
If the lesions are associated with itch, there is possibility of fungal infection.
Associated discharge or lymph node enlargement suggests sexually transmitted diseases (gonorrhea, lymphogranuloma venerum, granulare inguinale, etc).
If discharge is present examination of the discharge is required.
If fungal infection is suspected, skin scraping and staining with special stains for fungus is required.
If none of these features are present, a
skin biopsy will determine the disease process going on in the affected skin.
You need to visit a
dermatologist and venerologist for clinical examination and relevant investigations.
Thanks and take care
Dr Shailja P Wahal