While the cause of MA is incompletely understood, it is associated with, and probably caused by, friction and scratching with fingernails or implements such as towels or brushes.
Clinically, MA manifests as hyperpigmentation. The most common locations are the upper back and extensor upper extremities. A rippled pattern is sometimes seen. MA and lichen amyloidosis (LA) are believed to exist on a spectrum and are mainly differentiated by the nature of the primary lesion (macules and patches in MA and thin plaques in LA) and histopathologic findings. Some patients also display features of both MA and LA, which is termed "biphasic amyloidosis."
MA is generally a pruritic condition, but it may sometimes be asymptomatic. MA has been described in the setting of connective tissue diseases, primary biliary cholangitis, and multiple endocrine neoplasia type 2a.
E85.9 – Amyloidosis, unspecified
111032003 – Macular cutaneous amyloidosis
Differential Diagnosis & Pitfalls