Dermatology

Psoriasis

Definition

  • Psoriasis is a chronic, inflammatory disease characterized by well-demarcated, erythematous papules and plaques covered with silvery scales commonly on the scalp, elbows, knees, and trunk. 

Psoriasis on back1.jpg
Back and arms of a person with psoriasis
https://en.wikipedia.org/wiki/Psoriasis


Psoriatic plaque, showing a silvery center surrounded by a reddened border
https://en.wikipedia.org/wiki/Psoriasis

​Epidemiology

  • It affects 1–3% of the world’s population.
  • Approximately 30–40% of adults with psoriasis report signs and symptoms before 16 years of age.
  • Clinical manifestations occur at any age in childhood, although they are most frequently seen between 5 and 11 years of age.
  • In patients under 2 years of age, psoriatic diaper rash is the most common finding. Otherwise, in the pediatric population, generalized plaque-type psoriasis is most common, followed by guttate or “drop-like” psoriasis.
  • In pediatric plaque-type psoriasis, the scalp is the most frequently involved region and is the site of onset in 40–60% of patients younger than 20 years of age.
  • Intertriginous, facial, and anogenital involvement is also more common among children. Nail involvement has also been reported in 7–40% of patients under 18 years of age, with nail pitting as the most common change. 
  • Psoriasis is often familial.
  • Some believe it to be slightly more common in girls, although recent studies have shown a Female: Male ratio of 1:1.
  • Psoriasis has a bimodal peak of incidence, the first in childhood and the second after age 60. 

Pathophysiology

It is believed that psoriasis is an immune-mediated disease in which T-lymphocytes and dendritic cells play a central role.  Although drugs and infections may trigger psoriasis, the primary insult that initiates the disease is not always clear.  Erythema and scaling are the result of hyperproliferation and abnormal differentiation of the epidermis.  Cellular infiltrates in the epidermis and dermis of the lesions include neutrophils, T-lymphocytes and dendritic cells.  T-cells are activated with a predominance of CD8+ cells.  Studies suggest that dysfunction of regulatory T cells may be a factor in psoriasis.  Cytokines such as TNF-alpha, gamma interferon, interleukin IL-8, IL-6, and IL-12 are overexpressed.

Clinical Manifestations

  1. Psoriasis is a papulosquamous desquamative disorder of the skin.
  2. Lesions are usually round, well-circumscribed erythematous plaques covered with a silvery white scale.  Removal of the scale is most difficult at the center, where it is attached, resulting in pinpoint bleeding. This is referred to as Auspitz Sign.
  3. Lesions are most commonly seen on the scalp, elbows, knees, and gluteal crease. Facial involvement is seen more commonly in kids than adults.
  4. Fingernails may show pitting and itching may be present. Neither nail pitting nor pruritis are diagnostic of psoriasis, but both are helpful clues. In severe cases, you  may see dystrophic finger/toenails.
  5. In infants and toddlers it sometimes presents as psoriatic diaper rash, which is a bright red rash involving the creases of skin folds in the diaper area. This rash can then spread to the abdomen and legs.  This is thought to be the most common presentation in children less than 2 years of age.

Types

  1. Guttate psoriasis - is frequent in children and young adults. These lesions are round, up to 3 cm in diameter, and are found in a symmetric distribution on the trunk and proximal extremities.
  • -in a majority of patients, guttate psoriasis appears abruptly 1-3 weeks
  •  after an upper respiratory tract infection with Streptococcus. Therefore
  • obtaining a throat or perianal culture for Strep is recommended.

    Example of guttate psoriasis
    https://en.wikipedia.org/wiki/Psoriasis
  1. Koebner Phenomena – lesions appear at sites of local injury.
  2. Psoriatic Diaper Rash – well demarcated, bright red, shiny, in diaper distribution. Sometimes disseminates up the trunk and down the legs. It looks like normal diaper rash but is treatment resistant. Because it is uncommon to biopsy the skin of these infants, this diagnosis remains controversial.
  3. Plaque Type – the most common form of psoriasis. Plaques are symmetrically distributed, especially over elbows and knees.

Precipitating factors

  1. infection (B-hemolytic Strep and guttate psoriasis)
  2. virus (HIV)
  3. trauma (Koebnerization)
  4. drugs
  5. psychological stress

Diagnosis

Clinical diagnosis with the option of skin biopsy.  Features suggestive of psoriasis include a positive family history, no or mild pruritus, and localization of lesions to elbows, knees, and lower back.

Treatment

  1. Mild to moderate disease
    1. First line is liberal application of moisturizers/emollients such as petroleum jelly.
    2. Topical corticosteroids (low to medium potency if possible)
    3. Tar and Anthralin are old and messy, but they work.
    4. Calcipotriene (Vit D analog)
  2. Moderate to severe disease
  3. Phototherapy
  4. Methotrexate
  5. Phototherapy
  6. Retinoids
  7. Methotrexate, cyclosporine
  8. Alefacept, efalizumab, etanercept, infliximab
  9. Severe disease

References

  1. Morris, Anne. Childhood Psoriasis: A Clinical Review of 1262 Cases. Pediatric Dermatology 2001; 18:188-198.
  2. Wilson, Jill. Treatment of Psoriasis in Children: Is There a Role for Antibiotic Therapy and Tonsillectomy? Pediatric Dermatology Jan/Feb 2003; Vol. 20.
  3. Kerstin, Taniguchi A. Psoriasis Presentation Forms in Children. Peds Derm 1984.
  4. Arbuckle, HA. Psoriasis. Peds in Review Mar 1998; 19: 106-107.
  5. Sugiyama H., et. al. Dysfunctional blood and target tissue CD4+ CD25 high regulatory T cells in psoriasis. J Immunol. Jan 2005; 174(1):164-73.
  6. Sukhatme SV, Gottlieb AB. Pediatric psoriasis: updates in biologic therapies. Dermatol Ther 2009; 22: 34–39.