Atopic Dermatitis (Eczema)

Immunology, Skin No Responses »
Dec 262010
  • Atopic dermatitis is a chronic relapsing and remitting inflammatory skin disease characterized by dermatitis with typical morphology and distribution.
  • Eczema is a generic term for a constellation of clinical signs, whereas atopic dermatitis is a term that specifically connotes an allergic contribution to the etiology of the eczema.
  • The overall prevalence of atopic dermatitis in the United States is 17% among school-aged children, leading to considerable disease-related morbidity, including irritability, secondary skin infections, sleep disturbance, school absenteeism, and poor self-image.
History
  • Age of onset is a consideration, with 45% of affected individuals manifesting atopic dermatitis in the first 6 months of life, 60% by the first year, and 85% by school age.
  • Pruritus is a cardinal feature of eczema, often described as the “itch that rashes.” Scratching leads to further compromise in the skin barrier and augments inflammation.
  • Xerosis (dry skin) also involves nonlesional skin. (In other conditions, commonly mistaken for atopic dermatitis (seborrheic dermatitis, nummular eczema, and psoriasis), the uninvolved skin is generally healthy.)
  • Patients may have a personal and family history of atopy (asthma, hay fever, food allergy).
  • Exacerbating factors include food allergens (most frequently egg, milk, wheat, soy, peanut, tree nuts, shellfish) and inhalant allergens (e.g., pet dander, house dust mite).
  • Systemic involvement, with failure to thrive, chronic diarrhea, and/or recurrent infections should prompt consideration of underlying systemic disease, such as immunodeficiency (e.g., Wiskott-Aldrich syndrome, Netherton syndrome, immune dysregulation polyendocrinopathy enteropathy X-linked (IPEX) syndrome, and hyper-IgE syndrome), or malabsorption (e.g., zinc deficiency or cystic fibrosis).
Physical Examination
  • Xerosis
  • Morphology of lesions
    • Acute lesions: pruritic papules with excoriation and serous exudation
    • Chronic lesions: lichenified papules and plaques
    • Superficial linear abrasions from scratching
    • Indistinct lesional borders, unlike that of psoriasis

  • Areas of involvement. Although atopic dermatitis may appear anywhere on the body, characteristic patterns include:
    • Infants: cheeks, forehead, and extensor surface of extremities
    • Children/adolescents: flexor surface of extremities popliteal and antecubital fossae, and ventral surface of wrists and ankles Continue reading »
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Introduction to DiGeorge Syndrome

Genetics, Immunology No Responses »
Dec 142010

DiGeorge syndrome (DGS) now understood to be the chromosome 22q11.2 deletion syndrome was originally described as 3 syndromes found on 2 continents.Dr. DiGeorge was the first to provide clinical examples in humans that demonstrated the thymus was involved in immune function.

Pathophysiology

As the name chromosome 22q11.2 deletion syndrome implies, the syndrome is the result of a 2-3 million base pair (Mb) deletion on the long arm of chromosome 22. This area is prone to microdeletion because of the presence of nonallelic, flanking, low-copy repeat DNA sequences in the region, which lead to unequal crossing over between the two chromosome 22s during meiosis.

Frequency

Estimates of the incidence of chromosome 22q11.2 deletion syndrome range from 1 per 2000-4000 in the general population. It is a frequent cause of cleft palate and congenital heart defects.

Sex

Males and females appear to be equally affected.

Age

This is a congenital condition, but age at diagnosis largely depends on the severity and the types of birth defects. Thus, those with more serious cardiac defects, hypocalcemia, or both observed in classic DGS are diagnosed in the neonatal period. Recurrent infections usually present in patients older than 3-6 months. Some individuals without hypocalcemia who have normal immune Continue reading »

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Immunologic Drug Eruptions in Children

Immunology, Skin No Responses »
Nov 272010
Cutaneous adverse reactions to drugs are common in pediatric practice and often present a diagnostic challenge.
Pathogenesis:
The pathogenesis of most drug eruptions is not well understood. With few exceptions, eg, fixed drug eruption, the diagnosis cannot be based solely on the morphology of the eruption.

Clinical Features:
A drug rash may manifest as urticaria, a morbilliform exanthem, erythroderma, Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), photosensitivity, lichen planus, or vasculitis, all of which have other potential causes. A high index of suspicion for drug causation is important so that an offending drug is discontinued and avoided in the future, particularly in the case of life-threatening reactions such as anaphylaxis, the drug (anticonvulsant) hypersensitivity syndrome, SJS, and TEN. Conversely, it is important not to err by labeling a child as “allergic” to a widely used medication, such as penicillin. There are no standardized laboratory investigations that are diagnostic for drug allergy, and the value of allergy testing is largely restricted to cases of IgE-mediated penicillin hypersensitivity. Therefore, a detailed history, evaluation of the morphology of the rash, consideration of a differential diagnosis, and careful clinical judgment are essential.
The timing of the reaction may be helpful. Medications begun recently, particularly within the past Continue reading »
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