Multiple myeloma is a neoplastic plasma cell disorder characterized by clonal proliferation of malignant plasma cells in the bone marrow microenvironment, monoclonal protein in the blood or urine, and associated organ dysfunction (Palumbo and Anderson, 2011).

Familial Mediterranean fever (FMF) is divided into two phenotypes: type 1 and type 2. FMF type 1 is characterized by recurrent short episodes of inflammation and serositis including fever, peritonitis, synovitis, pleuritis, and, rarely, pericarditis and meningitis. The symptoms and severity vary among affected individuals, sometimes even among members of the same family. Amyloidosis, which can lead to renal failure, is the most severe complication, if untreated. FMF type 2 is characterized by amyloidosis as the first clinical manifestation of FMF in an otherwise asymptomatic individual.

Hereditary transthyretin (ATTR) amyloidosis is characterized by a slowly progressive peripheral sensorimotor and/or autonomic neuropathy as well as non-neuropathic changes of cardiomyopathy, nephropathy, vitreous opacities, and CNS amyloidosis. The disease usually begins in the third to fifth decade in persons from endemic foci in Portugal and Japan; onset is later in persons from other areas. Typically, sensory neuropathy starts in the lower extremities with paresthesias and hypesthesias of the feet, followed within a few years by motor neuropathy. In some persons, particularly those with early-onset disease, autonomic neuropathy is the first manifestation of the condition; findings can include: orthostatic hypotension, constipation alternating with diarrhea, attacks of nausea and vomiting, delayed gastric emptying, sexual impotence, anhidrosis, and urinary retention or incontinence. Cardiac amyloidosis is mainly characterized by progressive cardiomyopathy. Individuals with leptomeningeal amyloidosis may have the following CNS findings: dementia, psychosis, visual impairment, headache, seizures, motor paresis, ataxia, myelopathy, hydrocephalus, or intracranial hemorrhage.

Multiple self-healing palmoplantar carcinoma (MSPC) is characterized by recurrent keratoacanthomas in palmoplantar skin as well as in conjunctival and corneal epithelia. In addition, patients experience a high susceptibility to malignant squamous cell carcinoma (summary by Zhong et al., 2016).

In some affected individuals, the patches have characteristics of both lichen and macular amyloidosis. These cases are called biphasic amyloidosis.\n\nIn all forms of PLCA, the abnormal patches of skin usually arise in mid-adulthood. They can remain for months to years and may recur after disappearing, either at the same location or elsewhere. Very rarely, nodular amyloidosis progresses to a life-threatening condition called systemic amyloidosis, in which amyloid deposits accumulate in tissues and organs throughout the body.\n\nNodular amyloidosis is characterized by firm, raised bumps (nodules) that are pink, red, or brown. These nodules often occur on the face, torso, limbs, or genitals and are typically not itchy.\n\nIn macular amyloidosis, the patches are flat and dark brown. The coloring can have a lacy (reticulated) or rippled appearance, although it is often uniform. Macular amyloidosis patches are most commonly found on the upper back, but they can also occur on other parts of the torso or on the limbs. These patches are mildly itchy.\n\nLichen amyloidosis is characterized by severely itchy patches of thickened skin with multiple small bumps. The patches are scaly and reddish brown in color. These patches usually occur on the shins but can also occur on the forearms, other parts of the legs, and elsewhere on the body.\n\nPrimary localized cutaneous amyloidosis (PLCA) is a condition in which clumps of abnormal proteins called amyloids build up in the skin, specifically in the wave-like projections (dermal papillae) between the top two layers of skin (the dermis and the epidermis). The primary feature of PLCA is patches of skin with abnormal texture or color. The appearance of these patches defines three forms of the condition: lichen amyloidosis, macular amyloidosis, and nodular amyloidosis.