{
 "topic": "Alopecia Areata",
 "slug": "alopecia-areata",
 "category_id": 15273,
 "summary": "A T-cell-driven autoimmune, nonscarring hair loss producing sudden round patches on an otherwise normal scalp, the most common cause of hair loss in children.",
 "written_by": "claude-sonnet",
 "references": [
  {
   "title": "CURRENT Diagnosis and Treatment Pediatrics, Twenty-Fourth Edition",
   "author": "Hay, William W., Levin, Myron J., Deterding, Robin R., Abzug, Mark J.",
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    450
   ]
  },
  {
   "title": "Cover",
   "author": "Vitalsource Download",
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    4995
   ]
  },
  {
   "title": "Textbook of Pediatric Gastroenterology, Hepatology and Nutrition (Stefano Guandalini, Anil Dhawan)",
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  },
  {
   "title": "MedStudy Pediatrics Core 11th Edition 2024-2025",
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   "title": "Signs and Symptoms in Pediatrics",
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    56,
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  },
  {
   "title": "Ghai Essential Pediatrics, 9e (Vinod K Paul, Arvind Bagga)",
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  {
   "title": "The Harriet Lane Handbook (The Johns Hopkins Hospital)",
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   "title": "The Harriet Lane Handbook 22nd Edition (2020) (The Johns Hopkins Hospital)",
   "author": null,
   "pages": [
    251
   ]
  }
 ],
 "short": [
  {
   "title": "In short",
   "content": "- Alopecia areata is the most common cause of hair loss in children \u2014 a T-cell-driven autoimmune disorder in which loss of immune privilege of the hair follicle allows T-cell inflammation against anagen hairs, stopping hair growth; lifetime incidence is about 0.1-0.2% of the population (another source cites 1-2%), and more than half of affected patients are under age 20.\n- Presentation: sudden, complete hair loss in sharply circumscribed round or oval patches, typically on the scalp but possibly anywhere hair grows (eyebrows, eyelashes, body); the underlying skin looks normal, smooth, and shiny, sometimes with subtle erythema, and patches can appear over just a few days.\n- \"Exclamation-point hairs\" \u2014 short, broken hairs with a narrowed proximal shaft that are easily plucked at the patch margin \u2014 are a classic finding, along with occasional nail pitting, longitudinal striations, or leukonychia.\n- Unlike tinea capitis, alopecia areata has no clinically appreciable inflammation, scale, pruritus, or lymphadenopathy; if crusting, scaling, or redness is present, alopecia areata becomes less likely and tinea capitis should be considered instead (mycologic exam for Trichophyton tonsurans is warranted when uncertain).\n- Alopecia totalis is total loss of scalp hair; alopecia universalis is total loss of scalp, eyebrow, eyelash, beard, and body hair \u2014 a minority of patients progress to one of these forms.\n- Associated autoimmune conditions (though most affected children do not have one) include Hashimoto thyroiditis, type 1 diabetes, Addison disease, pernicious anemia, ulcerative colitis, myasthenia gravis, psoriasis, and vitiligo; alopecia areata is also linked to atopy and occurs more often in children with Down syndrome (5-10%) and celiac disease.\n- Poor prognostic features include childhood onset, ophiasis (band-like pattern along the scalp margin), atopy, and widespread/extensive hair loss.\n- About 50% of children with alopecia areata regrow hair completely within 12 months, though many of these will relapse in the future; regrowing hairs are initially grey before regaining color.\n- First-line treatment is topical corticosteroids; there is no strong evidence-based data that any therapy outperforms placebo, and dermatology referral is warranted for consideration of other treatments. Older children, adolescents, and young adults with longstanding localized hair loss have the best prognosis."
  }
 ],
 "long": [
  {
   "title": "Definition",
   "content": "Alopecia areata is a common, nonscarring form of alopecia characterized by sudden, complete hair loss in round or oval patches, most often on the scalp but also affecting eyebrows, eyelashes, or other body sites. In alopecia totalis, all scalp hair is lost; in alopecia universalis, all scalp, eyebrow, eyelash, beard, and body hair is lost."
  },
  {
   "title": "Epidemiology",
   "content": "Alopecia areata is the most common cause of hair loss in children. Estimates of lifetime incidence vary by source, from about 0.1-0.2% to 1-2% of the population. More than half of affected patients are younger than 20 years of age, and it is often seen in school-age children but is rarely seen in infants; onset can occur as early as birth. An increased incidence (5-10%) has been reported in patients with Down syndrome, and it is more common in children with celiac disease, even in the complete absence of GI symptoms, with a good response to a gluten-free diet reported in this group."
  },
  {
   "title": "Etiology",
   "content": "Alopecia areata is a T-cell-driven autoimmune disorder of unknown ultimate cause. In genetically susceptible individuals, loss of immune privilege of the hair follicle is hypothesized to allow T-cell inflammation against anagen hairs and follicles, halting hair growth; dense lymphocytic infiltration precedes hair loss. It has a genetic predisposition and can be associated with other autoimmune diseases, including Hashimoto (chronic lymphocytic) thyroiditis, type 1 diabetes mellitus, primary adrenal insufficiency (Addison disease), pernicious anemia, ulcerative colitis, myasthenia gravis, collagen vascular disease, psoriasis, and vitiligo \u2014 though most children with alopecia areata do not have a concomitant autoimmune disease, and evaluation for these should be guided by clinical suspicion. It is also associated with atopy."
  },
  {
   "title": "Clinical features",
   "content": "The typical lesion is a smooth, shiny, hairless, round or oval patch that appears suddenly, often over the course of days, with otherwise normal-appearing underlying skin; new lesions may show subtle erythema and can be pruritic. Scattered long hairs within the bald patch, or \"exclamation-point hairs\" (hairs with a narrowed proximal diameter, often shorter and lighter in color, and easily plucked at the margin) are characteristic. Nail changes can occur, including variable pitting, longitudinal striations, or leukonychia. In contrast to tinea capitis, there is no clinically appreciable inflammation, scale, pruritus, or lymphadenopathy. A minority of children progress to alopecia totalis (complete scalp hair loss) or alopecia universalis (total scalp and body hair loss)."
  },
  {
   "title": "Diagnostics",
   "content": "Alopecia areata is usually a clinical diagnosis based on the characteristic appearance of sharply circumscribed bald patches on otherwise normal skin, with exclamation-point hairs at the margin. When the presentation is ambiguous \u2014 particularly with crusting, scaling, redness, or associated lymphadenopathy \u2014 a mycologic examination looking for Trichophyton tonsurans should be performed to evaluate for tinea capitis, since inflammation is not a feature of alopecia areata and its presence lowers the likelihood of that diagnosis."
  },
  {
   "title": "Differential diagnosis",
   "content": "The differential includes tinea capitis (which, unlike alopecia areata, typically shows scale, crusting, redness, pruritus, or regional lymphadenopathy, and may show black dots from broken hairs), seborrheic dermatitis, atopic dermatitis, psoriasis, and trichotillomania (hair pulling, often related to obsessive-compulsive disorder). Because inflammation is not a feature of alopecia areata, its presence should shift suspicion toward one of these other diagnoses."
  },
  {
   "title": "Treatment",
   "content": "First-line therapy is topical corticosteroids. There is no strong evidence-based data that any available therapy performs better than placebo, and referral to dermatology is warranted for consideration of other treatment options."
  },
  {
   "title": "Complications",
   "content": "About 50% of affected children completely regrow their hair within 12 months, though as many may relapse in the future; regrowth is self-limited and can occur over several months to 1-2 years, with initially grey hairs regaining their normal color over time. A minority of patients progress to alopecia totalis or alopecia universalis. Poor prognostic features include onset in childhood, an ophiasis pattern (a band of hair loss along the scalp margin), association with atopy, and widespread/extensive alopecia. Older children, adolescents, and young adults with longstanding localized areas of hair loss have the best prognosis."
  }
 ],
 "clinical": [
  {
   "title": "Bedside evaluation",
   "content": "Examine any child with patchy hair loss for the characteristic features of alopecia areata: sharply circumscribed, smooth, round or oval patches of complete hair loss with otherwise normal-looking underlying skin, and exclamation-point hairs (short, tapered, easily plucked) at the margin. Check for nail pitting, striations, or leukonychia. Because inflammation is not a feature of alopecia areata, the presence of scaling, crusting, redness, pruritus, or regional lymphadenopathy should raise suspicion for tinea capitis instead, and warrants mycologic examination for Trichophyton tonsurans. Ask about atopy and, since alopecia areata can rarely accompany other autoimmune conditions (Hashimoto thyroiditis, type 1 diabetes, Addison disease, vitiligo, ulcerative colitis), pursue further evaluation only if the history or exam suggests one of these \u2014 most children with alopecia areata have no other autoimmune disease. Assess extent: single small patch versus multifocal or ophiasis-pattern loss versus progression toward alopecia totalis or universalis, since more extensive disease and childhood onset both predict a worse prognosis."
  },
  {
   "title": "Counseling and treatment",
   "content": "Start topical corticosteroids as first-line therapy for localized alopecia areata, and refer to dermatology for consideration of other treatments if the response is inadequate, since no therapy has strong evidence of outperforming placebo. Counsel families that about half of children regrow hair completely within about 12 months, though relapse is common, and that regrowing hairs are often initially grey before regaining color. Set expectations based on prognostic features present: localized, later-onset disease in an older child, adolescent, or young adult carries the best prognosis, while childhood onset, an ophiasis pattern, coexisting atopy, or widespread hair loss predicts a more guarded course, including possible progression to alopecia totalis or universalis."
  }
 ]
}