Two theories have been advanced to explain the origin of the amyloid deposits. These theories are not mutually exclusive and both could be responsible. This theory does not explain how the alpha type of keratin tertiary structure is degraded and converted into the beta pleated sheet configuration of amyloid. The incidence of MA is more common among Asians, Middle Easterners and South Americans. In many studies, macular amyloidosis seems to affect women more frequently than men.
Macular amyloidosis is a pruritic eruption that is variable in severity.
Frequently patients will seek medical attention because of the hyperpigmentation. The cardinal triad of this autosomal dominant syndrome is medullary thyroid carcinoma, pheochromocytoma, and hyperparathyroidism. In MA the amyloid deposits are usually found within the dermal papillae. The deposits can be minute, escaping detection. For this reason MA is part of the differential diagnosis for normal skin slide, sometimes called invisible dermatosis.