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A 35-year-old woman presents to the office for the evaluation of a rash on her knees bilaterally. The rash has been present for the past two months with intermittent itching, which has not improved with over-the-counter topical ointments. Past medical history is significant for inflammatory bowel disease, which is treated with 5-aminosalicylic acid. The rest of the history is noncontributory. The patient does not use tobacco, alcohol, or illicit drugs. Vitals are within normal limits. Physical examination shows a silver, scaly, erythematous plaque on the knees bilaterally that bleeds mildly on removing the scales. Which of the following histological findings are most likely to be seen on skin biopsy of this patient?

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Acanthosis p. 487

psoriasis p. 489

Arthritis p. 476

psoriatic p. 479

Plaques (skin) p. 487

psoriasis p. 489

Psoriasis p. 489

arthritis and p. 479

cyclosporine p. 118

etanercept for p. 501

hyperkeratosis/parakeratosis p. 487

infliximab/adalimumab for p. 501

methotrexate for p. 448

skin lesions p. 489

therapeutic antibodies p. 120

Psoriatic arthritis p. 479

psoriasis and p. 489

Scales (skin) p. 487

psoriasis p. 489


Psoriasis is a non-contagious, chronic autoimmune disease that causes skin inflammation, and is linked to other autoimmune deficiencies such as psoriatic arthritis.

It can be incredibly itchy and form silver plaques on the skin that can be embarrassing, and have both physical and psychological effects.

Afflicted reality TV star Kim Kardashian, and singer Cyndi Lauper have each spoken out on how psoriasis can have a significantly negative impact on the quality of life.

Normally, the skin is divided into three layers--the epidermis, dermis, and hypodermis.

The hypodermis is made of fat and connective tissue that anchors the skin to the underlying muscle.

Just above the hypodermis is the dermis, which contains nerves, sweat glands, lymph and blood vessels.

Just above the dermis is the epidermis.

The epidermis itself has multiple cell layers that are composed of developing keratinocytes - which are named for the keratin protein that they’re filled with.

Keratin is a strong, fibrous protein that allows keratinocytes to protect themselves from getting destroyed when you rub your hands through the sand at the beach.

Keratinocytes start their life at the lowest layer of the epidermis called the stratum basale, or basal layer, which is made of a single layer of small, cuboidal to low columnar stem cells that continually divide and produce new keratinocytes.

These new keratinocytes migrate upwards, forming the other layers of the epidermis.

As keratinocytes in the stratum basale begin to mature and lose the ability to divide, they migrate into the next layer, called the stratum spinosum which is about 8 to 10 cell layers thick.

The stratum spinosum also has dendritic cells lurking around, which are star-shaped immune cells constantly patrolling for invading microbes as part of the body’s immune defense system.

The next layer up is the stratum granulosum which is 3 to 5 cell layers thick.

Keratinocytes in this layer begin the process of keratinization, which is the process where the keratinocytes flatten out, and get rid of their intracellular structures and die, and in the process they create the epidermal skin barrier.


Psoriasis is an autoimmune disorder that affects the skin, which leads to the excessive proliferation of keratinocytes that don't mature correctly. It is characterized by thick, scaly, and silvery patches on the skin, known as plaques. These plaques are often itchy and painful, and they can crack and bleed. Psoriasis typically appears on the scalp, elbows, knees, and lower back, but it can also affect the nails, genitals, and mouth. Psoriasis treatment can include topical creams and ointments; immunosuppressive therapies, and UV phototherapy. For some individuals, there can be significant feelings of depression or anxiety, and a need for psychological counseling.


  1. "Robbins Basic Pathology" Elsevier (2017)
  2. "Harrison's Principles of Internal Medicine, Twentieth Edition (Vol.1 & Vol.2)" McGraw-Hill Education / Medical (2018)
  3. "Pathophysiology of Disease: An Introduction to Clinical Medicine 8E" McGraw-Hill Education / Medical (2018)
  4. "CURRENT Medical Diagnosis and Treatment 2020" McGraw-Hill Education / Medical (2019)
  5. "Psoriasis" The Lancet (2015)
  6. "New developments in the management of psoriasis and psoriatic arthritis: a focus on apremilast" Drug Design, Development and Therapy (2013)
  7. "Psoriasis Pathogenesis and Treatment" International Journal of Molecular Sciences (2019)
  8. "Psoriasis and its management" BMJ (2006)

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