Macular Amyloid
Author: Dr Lizzy Wasson
Chief Editor: Dr Daniel Keith
Amyloid is a keratinocyte-derived fibrillar material, which when it accumulates, can lead to a group of disorders known as amyloidosis. Macular Amyloid is a type of Primary Cutaneous Amyloidosis and occurs when amyloid accumulates only in the skin. Importantly, the presence of macular amyloid has no implication of systemic disease. The deposition of amyloid leads to patches of brown pigmentation which are often very itchy.
This condition is seen more commonly in patients of Asian descent (Fitzpatrick skin type IV and V). Some patients may have a family history of the condition. Although the exact cause of macular amyloid is unknown, factors such as repeated scratching, rubbing and friction to an area is thought to be related to its formation.
Macroscopic Appearance
Macular amyloid presents with brown pigmentation. The pigmented macules tend to form a ‘rippled appearance’, with macroscopically lighter dots surrounded by darker pigmentation
Dermoscopic Appearance
When examining macular amyloid under dermoscopy, the focus is on the distribution of the brown pigmentation. The brown pigmentation is thought to be caused by the melanin granules in the amyloid deposits which deposit in the papillary dermis and lead to basal hyperpigmentation and pigment incontinence.
Macular amyloid tends to have a classic distribution of a central sclerotic area (white or light brown) surrounded by brown pigmentation most commonly in distributions known as “spoke and wheel” or “leaf-like extensions”. In the “spoke and wheel” distribution brown pigmentation can be seen deposited in “rays” out from the central lighter area. Alternatively, “leaf-like extensions” can be more varied showing more polygonal projections from this central area. Hypopigmentation surrounding hair follicles may also be present.
The photographs below have been provided courtesy of Dr Rhys Daws, GP.
