Lichen sclerosus (LS) or balanitis sclerotica obliterans (BXO) is a disease that affects the skin of the genitals. In male patients, it can affect the foreskin, the glans penis, and the distal urethra. In the most severe cases, all the skin of the penis and all the urethra are affected. It is still not well understood why some patients develop Lichen Sclerosus, but it is now suspected that the maceration of the skin caused by the pooling of urine, recurrent skin infections that may trigger an exaggerated immune response, might be linked to the formation of lichen sclerosus. Often, patients affected by lichen sclerosus are also suffering from diabetes mellitus and have low levels of serum testosterone. 

The skin affected by lichen sclerosus becomes thicker, inelastic, and tends to become of a typical whitish color. As the skin is inelastic, it does not stretch during erections and cracks during sexual activity. The cracks are a source of pain, itching, and bleeding. When affected by lichen sclerosus, the foreskin becomes inelastic and unretractable in a clinical picture, also known as phimosis (tight foreskin); in the more severe cases, the inner layer of the foreskin may fuse with the mucosa of the glans. In the case of phimosis, it is impossible to retract the foreskin to clean the glans, and hygiene becomes consequently poor. It is therefore important to surgically correct the phimosis not only to improve sexual activity but also to reduce the risk of recurrent urinary tract infections and of developing penile cancer, which is strongly associated with poor genital hygiene. If the lichen sclerosus affects the urethra, this can manifest as a narrowing of the urethral tube and urination can become very challenging.