What is Macular Amyloidosis and How Is It Treated?

Macular amyloidosis is a skin manifestation in which discolored lumps develop, typically on the upper back, due to an accumulation of abnormal proteins called amyloids. Please continue reading to learn more about this condition, including the causes, symptoms, diagnosis, differential diagnosis, and treatment of macular amyloidosis.

What is primary localized cutaneous amyloidosis?

Primary localized cutaneous amyloidosis (PLCA) is a skin disorder in which patches of skin develop with abnormal color and texture. This occurs due to the formation of collections of amyloids (abnormal proteins) in the dermal papillae at the dermal-epidermal junction (projections at the border of the dermis and epidermis, the two upper layers of skin).

The skin patches in primary localized cutaneous amyloidosis are of three types:

Macular amyloidosis
Lichen amyloidosis
Nodular amyloidosis

Some people have patches that look like both lichen and macular amyloidosis. This is known as biphasic amyloidosis.

Very rarely nodular amyloidosis (a type of cutaneous amyloidoses) can progress to systemic amyloidosis. This is a potentially life-threatening disorder in which there is a widespread formation of amyloid deposits in many organs and tissues.

What is macular amyloidosis?

As mentioned above, macular amyloidosis is one of three types of primary localized cutaneous amyloidosis (PLCA). These are skin disorders in which abnormal amyloid filaments are deposited in the papillary dermis.

What causes macular amyloidosis?

Macular amyloidosis is believed to occur due to a mix of environmental and genetic factors. Risk factors include prolonged periods of friction (rubbing or scratching the skin). There are case reports of macular amyloidosis caused by long-term back scratching with a nylon brush.

However, the exact way in which the amyloid deposits form at a cellular level in the papillary dermis is not entirely understood.

What do macular amyloidosis patches look like?

The patches associated with macular amyloidosis are dark-brown or blue-gray in color and flat. They can be uniform in appearance or have a rippled or lacy effect. The patches tend to be mild to severely itchy.

Macular amyloidosis patches typically develop on the upper back but can also form on other parts of the trunk and limbs. The patches are usually symmetrically distributed on either side of the back. Less commonly, the patches can occur on the face, neck, collarbones, underarms, and breasts.

Is macular amyloidosis rare?

Primary localized cutaneous amyloidosis (PLCA) is most commonly seen in people from South America, Southeast Asia, and the Middle East. Darker skin tones (Fitzpatrick skin types IV and V) are more prone to developing primary localized cutaneous amyloidosis.

It is unclear how prevalent the condition is, but most cases of primary cutaneous amyloidosis are diagnosed in early adulthood. It appears that primary localized cutaneous amyloidosis affects women more frequently than men, but this could be because women tend to seek medical attention more often due to cosmetic concerns caused by cutaneous macular amyloidosis.

Is macular amyloidosis inherited?

In most cases, primary cutaneous amyloidosis is not inherited, meaning it occurs in people with no family history of the condition.

However, around 10% of cases are familial primary cutaneous amyloidosis, meaning the condition runs in the family.

Studies on familial primary localized cutaneous amyloidosis show that macular and lichen amyloidosis can be inherited through autosomal dominant or recessive mutations. The former means an affected person has one parent who suffers from familial primary localized cutaneous amyloidosis. The latter means both parents are carriers (each carries one copy of the mutated gene for primary cutaneous amyloidosis). This gives their children a genetic predisposition for the condition; however, the parents themselves do not show symptoms of primary cutaneous amyloidosis.

There are also case reports of associations between cutaneous amyloidosis, atopic dermatitis, and multiple endocrine neoplasia 2A (MEN2A).

Is macular amyloidosis serious?

While the collection of the amyloid material in the skin itself is harmless, macular amyloidosis can significantly impact a person’s quality of life due to cosmetic concerns. This is due to the pigmentation in macular amyloidosis as well the thickened skin and severely itchy patches.

What can macular amyloidosis be confused with?

Conditions such as dermatomyositis, scleroderma, and mycosis fungoides can cause poikiloderma (skin discoloration), which can be confused with macular amyloidosis or lichen amyloidosis. A skin biopsy can help confirm the diagnosis of cutaneous amyloidosis or something else.

How is macular amyloidosis diagnosed?

Dermatologists can diagnose macular amyloidosis based on the characteristic appearance of the amyloid protein with a dermatoscope (examining the skin surface with a microscope).

In macular amyloidosis, the amyloid deposits appear as a central white or brown area with radiating dots, streaks, or projections. In some cases, a skin biopsy may be necessary to confirm the diagnosis.

Is macular amyloidosis treatable?

There is no standardized treatment for amyloid formation in the skin. Various treatment modalities are used, including a laser for macular amyloidosis (pulsed dye laser, fractional laser, and Q switched Nd: YAG laser). Other treatments offered to patients with macular and papular amyloidosis include phototherapy, dermabrasion, electrodesiccation, cryosurgery, TENS (transcutaneous electrical nerve stimulation), occlusive dressings, topical medications, and systemic medications. There is no solid scientific evidence that any of these therapies are more effective than the others.

The main goal of macular amyloidosis treatment is usually providing relief from itching. Some of the medications that may be prescribed to people with macular amyloidosis include: