Idiopathic guttate hypomelanosis

Idiopathic guttate hypomelanosis is a common condition characterised by the presence of numerous, small, white macules found predominantly on the shins and forearms. It is seen firstly in middle-aged, fair-skinned women, but occurs increasingly with age in both sexes as well as dark-skinned individuals with a history of long-term sun exposure.

This chapter is set out as follows:

• It is thought to be an inevitable part of ageing, with a gradual reduction in melanocytes
• UV-damage may play a role 
• Inherited factors may be relevant as lesions appear to be more common in family members

• Idiopathic guttate hypomelanosis is seen far more frequently in women of a younger age than in men. However, with increasing age and sun exposure, it is found almost equally in elderly men and women
• It predominantly affects fair-skinned individuals, but it can be seen in older, darker-skinned individuals 

Distribution

• ​Although most commonly found on the shins and extensor forearms, it can also affect other sun-exposed areas such as the face and neck 

Morphology

• Multiple, small, porcelain-white macules
• Lesions are usually smooth and have a well-defined edge

• There is no known effective treatment