What is the difference between psoriasis and lichen planus

Differential diagnosis of psoriasis and lichen planus plays an important role in dermatology. These two diseases have similarities, but there are also many differences. Today we will talk about the most basic ones.

What you need to know about psoriasis

Psoriasis is lichen. Despite the fact that in the minds of many, lichen is associated exclusively with something infectious, psoriasis has a second name “squamous lichen”, although it does not pose a threat to others. The disease often recurs and reduces the quality of life. It is impossible to completely get rid of psoriasis, but you can remove unpleasant symptoms with the help of ointment and lifestyle correction.  

The number of patients with psoriasis is increasing every year. Scaly lichen has several typical symptoms:

  • pink spots protruding above the surface of the skin, which are peeling;
  • there are white scales on these spots;
  • psoriatic plaques tend to merge;
  • itching of varying degrees of intensity – from a slight tingling sensation to the desire to scratch the skin to blood;
  • white exfoliating spots on the nails;
  • dryness and flaking.

Most often, psoriasis appears on the elbows, knees, head and groin. It can appear for the first time at any age; it is not uncommon for the first symptoms to occur in puberty and at the age of 20 to 30 years. Scientists believe that the main cause of psoriasis is an autoimmune process, when the immune system attacks skin cells and causes chronic inflammation.  

How to recognize lichen planus

The fact that a person has this particular type of lichen can be indicated by flat papules of red or purple color. At the very beginning of the disease, the papules are very small, they reach a size of no more than 2-4 mm, while their surface shines slightly in mixed light. Most often, rashes appear on the flexion areas of the arms and legs, on the trunk, genitals, including mucous membranes, and also in the mouth. As with psoriasis, the patient desperately wants to comb the affected areas.

LP is thought to be caused by autoimmune factors as well as psoriasis. The trigger for the appearance of rashes can be a variety of factors, for example, hepatitis C or taking certain medications.

How to understand whether lichen or psoriasis is in front of us

To summarize all of the above, we can distinguish several similar features of the two diseases:

  • autoimmune nature;
  • rash in the form of papules;
  • itching;
  • red papules;
  • the folds of the arms and legs are often affected.

The question arises of how to distinguish psoriasis from lichen. Diseases have several differences:

  • psoriatic plaques peel off, scales can be seen on the surface, and with lichen planus, the surface of the papules is smooth;
  • psoriasis does not occur on mucous membranes, but LP often affects the oral cavity and mucous surfaces of the genitals;
  • plaques of psoriasis are larger than those that form with lichen;
  • if lichen planus affects the scalp, scarring may occur.

The psoriatic triad

During the examination, if the doctor is faced with the task of confirming or refuting psoriasis, the specialist assesses the presence of signs of the psoriatic triad:

  • the phenomenon of a stearin spot – when scraping from the surface of the spot, soft whitish scales are separated;
  • the phenomenon of the psoriatic film – when the scales are scraped off, the pink smooth surface of the plaque is exposed;
  • the phenomenon of punctate bleeding – with complete scraping of the papules, small droplets of blood appear, resembling dew.

Since the treatment of psoriasis and LP is significantly different, it is important to see a doctor at the first manifestations so as not to waste time and aggravate the situation.  

event_note October 5, 2021

account_box Dr. Peter B Milburn

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