Ash-leaf spots

Hypomelanotic macules are otherwise known as ash-leaf spots due to their resemblance to Sorbus aucuparia, or mountain-ash, leaves. These macules have a strong association with tuberous sclerosis and are often multiple and present in the vast majority of individuals with the condition (up to 97% ). As such the presence of more than three hypomelanotic macules prompts further investigation.

Pathology

Histologically, melanocytes are distributed normally within the stratum basale of the epidermis but contain a reduced level of melanin .

Differential diagnosis

Important differentials to consider include:

• nevus anaemicus: mediated by vasoconstriction
• achromic nevus: a form of congenital mosaicism, where some melanocytes have a reduced ability to generate melanin