Difference Between Seborrheic Dermatitis and Psoriasis

Key Difference – Seborrheic Dermatitis vs Psoriasis
 

Dermatological conditions are perhaps the most worrisome diseases in the world. It makes the patient both mentally and physically ill and sometimes more severe cases can even interrupt his or her social life. Psoriasis and seborrheic dermatitis are two such dermatological disorders that can be extremely distressing. Psoriasis is a chronic multisystem disease with skin and joint manifestations. On the other hand, seborrheic dermatitis can be considered as the inflammation of the skin of hairy regions.  Arthropathy is seen as a comorbidity in psoriasis, not in seborrheic dermatitis. This can be considered as the key difference between seborrheic dermatitis and psoriasis.

CONTENTS

1. Overview and Key Difference
2. What is Seborrheic Dermatitis
3. What is Psoriasis
4. Similarities Between Seborrheic Dermatitis and Psoriasis
5. Side by Side Comparison – Seborrheic Dermatitis vs Psoriasis in Tabular Form
6. Summary

What is Seborrheic Dermatitis?

The term dermatitis is used to describe a condition where the skin is inflamed. Seborrheic dermatitis is one such condition where the skin of hairy areas is inflamed forming characteristic greasy yellow scales.

Presentation

• Red scaly or exudative eruptions on the skin of scalp, ears, face, and eyebrows
• Dry scaly petaloid lesions on the skin of interscapular or presternal regions
• Intertriginous lesions in the armpits, umbilicus or groins

Causes

• Family history of Seborrheic dermatitis
• HIV

Complications

• Furunculosis
• Superimposed candida infection

Treatment

The therapy is only suppressive; therefore, the patient should be made aware about the possible relapses.

• Topical imidazoles are used as the first line drugs.
• Use of sulfur diluted in salicylic acid has been proven to be effective
• A topical lithium preparation can be used for the facial rashes

What is Psoriasis?

Psoriasis is a chronic multisystem disease with skin and joint manifestations.

Precipitating Factors

• Trauma
• Infection
• Hormonal imbalances such as hypoparathyroidism
• Drugs such as antimalarials and beta blockers
• Cigarette smoking and alcohol

Histological Features

• Parakeratosis
• Irregular thickening of the epidermis. But the epidermis over the dermal papillae is depleted, which results in bleeding when scratched or the scales are removed. This is called auspitz.
• Polymorphonuclear leukocyte microabscesses
• Dilated and tortuous capillary loop
• Infiltration of the upper epidermis by T lymphocytes

   Clinical Features

• Presence of plaques
• Scaling
• Erythema
• Pustules can appear sometimes on the skin of plantar and palmar surfaces
• Pitting of nails

The onset of psoriasis happens usually at the early adulthood. In pediatric cases, the presentation is atypical.

There can be a family history of psoriasis. Any physiological stress such as trauma and infection can trigger the pathological processes that give rise to this condition. A hallmark feature of psoriasis is the Koebner’s phenomenon where the lesions first appear at a site of minor trauma. These lesions are not itchy and are cleared by the exposure to the sun. Associated arthropathy is a common comorbidity.

Different Forms of Psoriasis

Guttate Psoriasis

This usually occurs in adolescents within few weeks after a hemolytic streptococcal infection. The lesions disappear spontaneously.

Pustular Psoriasis

Can occur as chronic deep seated lesions or generalized pustular psoriasis.

Flexural Psoriasis

This is the form of psoriasis that occurs in places such as submammary, axillary and anogenital folds. Scales are rare but there is a characteristic glistening nature.

Napkin Psoriasis

This appears in the area covered by the diapers. Babies who get napkin psoriasis are more likely to get psoriasis in the adult life.

Erythrodermic Psoriasis

Erythrodermic psoriasis is a rare form of psoriasis which is triggered by the irritant effect of chemicals such as tar.

Complications of Psoriasis

Psoriatic Arthropathy

Arthritis is a common complication of psoriasis which is approximately seen among 5% of the psoriatic patients. Usually, the terminal interphalangeal joints of the toes and fingers are affected. In some occasions, the symptoms and clinical features of psoriatic arthropathy mimic rheumatoid arthritis in which case large joints such as sacroiliac joint are affected.

Investigations

• Biopsies are rarely done.
• In Guttate psoriasis, throat swabs are taken to find the presence of beta hemolytic streptococci
• Skin scrapings and nail clippings are required to exclude tinea
• Radiography is necessary to assess the associated arthropathy

Management

• Drugs such as Vitamin D analogs, calcipotriol and tacalcitol can be given
• UV radiation therapy
• Treatment with local retinoids or local corticosteroids

 What are the Similarities Between Seborrheic Dermatitis and Psoriasis?

• Both conditions are dermatological disorders.
• The appearance of scales is usually seen in both conditions.

What is the Difference Between Seborrheic Dermatitis and Psoriasis?

Summary – Seborrheic Dermatitis vs Psoriasis

Psoriasis and seborrheic dermatitis are fairly common skin disorders mostly affecting patients in their early adulthood. Psoriasis is a multisystem disorder with joint manifestations whereas seborrheic dermatitis is the inflammation of the skin of hairy areas. In spite of the high number of shared clinical features, these two diseases can be easily distinguished from each other by the joint manifestations which are only seen in psoriasis. This is also the key difference between seborrheic dermatitis and psoriasis.

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References:

1. Buxton, Paul K. ABC of dermatology. London: BMJ , 2007. Print.

Image Courtesy:

1. “Seborrhoeic dermatitis head” By Amras666 – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Psoriasis on back1” By Psoriasis_on_back.jpg: User:The Wednesday Island (of the English Wikipedia)derivative work: James Heilman, MD (talk) – Psoriasis_on_back.jpg (CC BY-SA 3.0) via Commons Wikimedia