SNP Shot: Genomic Insights

Primary localized cutaneous amyloidosis (PLCA) is a skin condition where abnormal protein deposits, called amyloids, accumulate within the skin, specifically in the dermal papillae, which are the wave-like structures between the dermis and epidermis (the two upper layers of skin). The main symptom of PLCA is the appearance of skin patches with altered texture or color. These patches are categorized into three types: lichen amyloidosis, macular amyloidosis, and nodular amyloidosis.

Lichen amyloidosis presents as intensely itchy, thickened skin patches with numerous small bumps. These patches are reddish-brown and scaly. They typically appear on the shins, but may also affect the forearms, other leg areas, or other body parts.

Macular amyloidosis is characterized by flat, dark brown skin patches. The pigmentation can have a lacy or rippled appearance (reticulated), though it is often uniform. These patches are most commonly found on the upper back, but can occur on the torso or limbs. Macular amyloidosis patches are usually only mildly itchy.

Nodular amyloidosis involves firm, raised bumps (nodules) that are pink, red, or brown in color. These nodules often appear on the face, torso, limbs, or genitals and are typically not itchy.

Some individuals may exhibit patches with features of both lichen and macular amyloidosis, which is termed biphasic amyloidosis.

In all forms of PLCA, the unusual skin patches typically develop in middle adulthood. They can persist for months to years and may reappear after disappearing, either in the same location or elsewhere. In rare instances, nodular amyloidosis can progress to systemic amyloidosis, a life-threatening condition where amyloid deposits build up in various tissues and organs throughout the body.

Inheritance:

Most PLCA cases are not hereditary and occur sporadically in individuals with no family history of the condition. When PLCA does run in families, it is usually inherited in an autosomal dominant manner. This means that only one copy of a mutated OSMR or IL31RA gene in each cell is enough to cause the condition. In these instances, the affected person has one parent who also has the condition. Rarely, PLCA caused by a mutation in the OSMR gene is inherited in an autosomal recessive manner. This means that both copies of the gene in each cell must be mutated. The parents of an individual with an autosomal recessive condition each carry one copy of the mutated gene, but generally do not exhibit any signs or symptoms of the condition themselves.