Psoriasis and Dermatitis — the Quick Differences and Similarities.
Side by side comparison
Plaque psoriasis. Image from: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 1997. Psoriasis. Dermnet NZ website.
Dermatitis. Image from: Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand,1997. Dermatitis. Dermnet NZ website.
Psoriasis
Key aspects
Its prevalence is about 2-4% in the population, but it is believed to be underestimated.
Can presents itself as a bimodal distribution (2 types of psoriasis).
Lifelong condition that fluctuates in severity.
Dermatitis (Eczema)
Key aspects
Dermatitis has been found to affect 1 in 5 people.
Does not have a bimodal distribution, and can start as early as 2 weeks of age.
Lifelong condition that fluctuates in severity.
Etiological factors
Multifactorial and is classified as an immune-mediated inflammatory disease (IMID).
Increase in epidermal turnover with inflammation causing immature and abnormal skin surface.
Genetics is one of the main factors for severity.
Etiological factors
Complex interactions between genetics, inflammation and the environment the person is living in.
Presents with epidermal changes: spongiosis and intracellular oedema. The skin barrier is dysregulated where proteins are deficient and increased susceptibility to infections.
Family history and dysregulated immune system.
Aggravating factors
Family history and genetics.
Cold and dry weather.
Streptococcal infections often induce psoriasis, especially for psoriasis guttae.
Trauma may induce psoriasis on the flexor surface; this is known as the koebner phenomenon.
Medications: beta-blockers, NSAIDs, hydroxychloroquine, lithium and withdrawing steroid such as prednisone.
Excess smoking and/or alcohol consumption.
Metabolic syndrome.
Sun exposure, although the sun is found to be beneficial and a type of treatment.
Stress.
Aggravating factors
Family history and genetics
Cold and dry weather.
Age and health condition.
Sand from the beach or sandpits.
Bathing too many times may exacerbate dermatitis. Utilise lukewarm water, and showers are shown to be better. Use soaps that the dermatologist recommends.
Certain clothes may exacerbate dermatitis. Avoid coarse fibres and wear soft and smooth garments.
Avoid any irritants such as chemicals, incontinence, dust, overexposure of water, solvents, detergents, and physical injury.
Staphylococcus aureus or Streptococcus pyogenes infections.
Occupation exposure.
Clinical features
Psoriasis is seen as a well-defined red and scaly plaque.
The scales have a white/silver appearance, except there are no scales when the lesion appears in the folds such as the genital and under the breast area.
It is commonly distributed symmetrically on the body and is seen on the scalp, elbows, knees and lower back.
Extensor surfaces of the body.
Not always itchy, but can be very itchy, which may cause lichenification due to scratching.
Nail abnormalities are very common.
Auspitz sign positive.
Clinical features
Dermatitis presents as a patchy, red, poorly defined rash.
No distinct silvery scales.
Found in the cubital fossae (the flexure between the forearm and the biceps), the popliteal fossae (behind the knees), and the face, but can be found anywhere on the body if it is severe enough.
Flexors surface of the body.
Patients with dermatitis experience itching of the skin, and in some cases, the itching may be so severe that patients may scratch the top layer off, which is called excoriation of the skin. Itching may accelerate the epidermal changes and thickens the top layer of the skin; this is called lichenification.
Dryness of the skin is common.
Auspitz sign negative.
Asthma and hay fever may also be present.
Variants
Chronic plaque psoriasis (most common, 90% of psoriasis presentations).
Scalp psoriasis.
Guttate psoriasis.
Palmoplantar psoriasis.
Nail psoriasis.
Genital psoriasis.
Flexural psoriasis.
Pustular psoriasis.
Erythroderma psoriasis.
Children with psoriasis.
Variants
Endogenous
Endogenous dermatitis is more common and is associated with genetic susceptibility.
Atopic dermatitis: seen in children with a history of asthma or hay fever.
Seborrhoeic dermatitis or dandruff: may be infantile or is seen in teens/adults, is mostly associated with Malassezia yeasts and inflammation.
Nummular dermatitis: are scattered looking coins-shape rashes.
Stasis or gravitational dermatitis: comes from poor blood flow around the lower legs.
Asteatotic dermatitis or dry skin: cracked paving stone appearances, arises mostly on the lower legs.
Pompholyx dermatitis: small, fluid-filled blisters appear on the palms, fingers and soles of feet.
Otitis externae: dermatitis affecting the external ear canal.
Exogenous
Exogenous dermatitis is more due to external factors.
Irritant contact dermatitis: can be done due to friction, liquids such as solvents and detergents. Is seen to be associated more with people who have a tendency to display atopic dermatitis.
Allergic contact dermatitis: dermatitis caused by elements that people do not generally react to. Patch testing can be done.
Otitis externae: dermatitis affecting the external ear canal.
Complications
Lichenification of the skin.
Psoriatic arthropathy.
Infection of the skin.
People with psoriasis are more likely to develop metabolic syndromes such as obesity, type 2 diabetes, high blood pressure, gout and cardiovascular diseases.
Other autoimmune conditions as psoriasis are linked to a dysregulated immune response.
Inflammatory conditions, such as Crohn’s disease.
Psychological distress.
Complications
Lichenification of the skin.
Hyperpigmentation.
Lipodermatosclerosis occurs, especially in stasis dermatitis.
Ulceration.
Infections of the skin such as impetiginisation (secondary infection causing yellow crusting).
Cellulitis.
Psychological distress.
Treatments
Biopsies are essential in making sure of the diagnosis. It is essential to explain to the patient that psoriasis is a lifelong/chronic disease and takes time and patience to treat. Referral to a specialist may be necessary. An important aspect of treatment is to identify and tackle any contributing factors.
Treating psoriasis include:
Avoid aggravating factors and lifestyle modification.
Use of emollients.
Use of topical anti-inflammatory or corticosteroids.
Coal tar preparation.
Vitamin D analogues.
Phototherapy.
Systemic approach, such as methotrexate.
Use of biologics, such as monoclonal antibodies (mAb).
Psychological treatment and social support.
The severity will dictate what type of treatment should be used and the type of medication combinations.
Treatments
Biopsies are essential in making sure of the diagnosis. It is essential to explain to the patient that dermatitis is a lifelong/chronic disease and takes time and patience to treat. Referral to a specialist may be necessary. An important aspect of treatment is to identify and tackle any aggravating or contributing factors.
Treating dermatitis include:
Avoid aggravating factors and lifestyle modification.
Use of emollient, the greasier the better (helps to avoid the dryness).
Wet dressings over emollient to prevent further scratching
Use of topical anti-inflammatory, corticosteroids or immunomodulators.
Investigations of genetics and treatment of allergies.
Pimecrolimus cream.
Antibiotics against infections that aggravate dermatitis.
Antihistamines.
Other treatments such as systemic steroids, methotrexate, phototherapy.
Exogenous dermatitis: remove the irritant from the skin and wear protective clothing.
Psychological treatment and social support.
The severity will dictate what type of treatment should be used and the type of medication combinations.
Published 30th December 2020. Last reviewed 1st December 2021.
Reference
Alpay-Kanıtez N, Çelik S, Bes C. Polyarthritis and its differential diagnosis. Eur J Rheumatol. 2018;6(4):167-173. doi:10.5152/eurjrheum.2019.19145
A PPOC/CHICO Learning Community & Integration Program © 2014 Pediatric Physicians’ Organization at Children’s (PPOC). Atopic Dermatitis Didactic Webinar: Bringing Basic Dermatology Care to the Pediatric Medical Home. Thursday May 4, 2017. Accessed November 30, 2020.
Armstrong AW. Psoriasis. JAMA Dermatol. 2017;153(9):956. doi: 10.1001/jamadermatol.2017.2103
David Zelman, MD. Enthesopathy and Enthesitis. WebMD. Reviewed April 30, 2019. Accessed November 30, 2020.
Dr Amanda Oakley, Dermatologist, Hamilton, New Zealand,1997. Dermatitis. Dermnet NZ website. https://dermnetnz.org/topics/dermatitis/. Accessed November 30, 2020.
Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand, 1997. Psoriasis. Dermnet NZ website. https://dermnetnz.org/topics/psoriasis/. Updated August, 2014. Accessed November 30, 2020.
Mayoclinic authors. Dermatitis. Mayoclinic website. https://www.mayoclinic.org/diseases-conditions/dermatitis-eczema/symptoms-causes/syc-20352380. Updated June 11, 2019. Accessed December 3, 2020.
Mayoclinic authors. Psoriasis. Mayoclinic website. https://www.mayoclinic.org/diseases-conditions/psoriasis/symptoms-causes/syc-20355840. Updated May 2, 2020. Accessed December 3, 2020.
Plastic Surgery Key Authors. Eczema and Dermatitis. Plastic Surgery Key website. https://plasticsurgerykey.com/eczema-and-dermatitis/#figureanchor7-1. Accessed November 30, 2020.
Rubén Queiro, Patricia Tejón, Sara Alonso, Pablo Coto, Age at disease onset: a key factor for understanding psoriatic disease. Rheumatology. 2014;53(7):1178-1185. https://doi.org/10.1093/rheumatology/ket363
Stephanie S. Gardner, MD. Is Psoriasis an Autoimmune Disease? WebMD website. https://www.webmd.com/skin-problems-and-treatments/psoriasis/psoriasis-autoimmune. Reviewed September 28, 2019. Accessed December 3, 2020.
