Psoriasis versus Rosacea: What are the similarities and differences?

• Psoriasis.

  Psoriasis is a systemic and chronic inflammatory skin eruption. It presents as thick, red plaques that shed skin. Psoriasis is characterised by an excessive renewal and accumulation of epidermal cells, leading to a local inflammation . This disease primarily affects adults, with a peak onset typically between the ages of 20 and 40. Its manifestation is triggered by a combination of several risk factors. These include the immune system, genetic predisposition, and environmental factors. Symptoms are primarily located on the torso, elbows, knees, scalp, and rarely on the face.

• Rosacea.

  Rosacea is a chronic skin condition that primarily manifests on the face, particularly on the forehead, nose, cheeks, and chin. It is characterised by widespread and extensive redness, as well as the dilation of small blood vessels in the face, which often makes them visible. In addition to redness, rosacea is often accompanied by other symptoms, such as hot flushes, increased skin sensitivity, a burning sensation, and tingling in the affected areas.

  This skin condition tends to progress in cycles. Symptoms may appear for weeks or months, then disappear before re-emerging more prominently. Over time, rosacea can evolve and present more severe symptoms, such as red pimples filled with pus, a marked thickening of the skin, or even eye involvement.

These two skin diseases exhibit certain similarities.

• Genetic predispositions.

  About 30% of psoriasis cases are said to be familial and appear during adolescence. There is not a single gene responsible for psoriasis disease but rather a set of genes. According to genetic linkage studies, PSORS1 has been identified as the main psoriasis susceptibility locus, contributing to about 35 to 50% of the disease's heritability. The PSORS1 region also encompasses the CDSN gene which codes for corneodesmosin, a desmosomal protein involved in the cohesion and desquamation of keratinocytes. This locus is associated with an early onset of the disease.

  It is estimated that nearly 30% of individuals suffering from rosacea have a family history of this condition, leading researchers to suggest the involvement of as yet unidentified genes. One hypothesis considered is the prevalence in individuals with rosacea of certain receptors, such as the TRPA1 and TRVP1 receptors, which are involved in inflammatory processes.

• Non-communicable diseases.

  There are many misconceptions surrounding psoriasis and rosacea, particularly the belief that they are contagious. This misinformation often leads to social isolation for the affected individual. It is crucial to remember that both these conditions are not contagious.

• A psychological impact.

  These two diseases exhibit visible symptoms, notably lesions, red patches or pimples. These can have a significant psychological impact and can negatively affect the quality of life of patients.

• Incurable diseases.

  Psoriasis and rosacea are two conditions that progress in cycles. Symptoms may appear for weeks or months, then disappear before re-emerging more pronounced. Although there are treatments to soothe the symptoms of the psoriasis and the rosacea, none of them can permanently cure these diseases.

Although these two diseases exhibit numerous similarities, they differ in certain aspects.

• Clinical manifestations.

  The psoriasis is characterised by the appearance of red patches covered with scales. Indeed, these are the result of an excessive proliferation of keratinocytes. Moreover, psoriasis patches are well defined. Conversely, rosacea presents redness due to the bursting of blood vessels.

• The affected areas.

  These two conditions do not affect exactly the same areas of the body. Rosacea is solely concentrated on the face, whereas psoriasis can affect the face but also any other part of the body.

• The associated symptoms.

  Beyond the presence of redness, psoriasis can cause itching, a burning sensation and pain in the affected areas. On the other hand, in the case of rosacea, there is often a flushing, increased skin sensitivity, as well as sensations of burning and tingling.

• BARKER J. N & al. Psoriasis and genetics. Advances in Dermatology and Venereology (2020).

• OKADA Y. The current landscape of psoriasis genetics in 2020. Journal Pre-Proof (2020).

• ALI F. & al. Rosacea. British Journal of Hospital Medicine.(2021).