Síndrome de María Antonieta, un raro caso de canicie súbita

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Figure.A, Singular patch of alopecia areata on the left parietal side (X) of the patient's scalp. B, Total canities. The time lapse between A and B was 6 months (normal photodocumentationinterval).Marie Antoinette syndrome designates the condition in which scalp hair suddenly turns white. The name alludes to the unhappy Queen Marie Antoinette of France (1755-1793), whose hair allegedly turned white the night before her last walk to the guillotine during the French Revolution. She was 38 years old when she died. Although the actual incidence is rare, this stigmatizing phenomenon, which has captured storytellers' imagination like few other afflictions, occurs to protagonists as a sign of grave sorrow in religious texts as early as the Talmud. History also records that the hair of the English martyr Sir Thomas More (1478-1535) turned white overnight in the Tower of London before his execution. More modern accounts refer to the turning white of hair in survivors of bomb attacks during World War II. In 1957, an American dermatologist witnessed a 63-year-old man's hair turn white over several weeks after he had fallen down some stairs. The patient noticed loss of hair but no bald patches and 17 months later had extensive vitiligo.1 The term canities subita has also been used for this disorder.2- 3 Today, the syndrome is interpreted as an acute episode of diffuse alopecia areata in which the very sudden “overnight” graying is caused by the preferential loss of pigmented hair in this supposedly immune-mediated disorder.4 This observation has led some experts to hypothesize that the autoimmune target in alopecia areata may be related to the melanin pigment system.5
The etiology of alopecia areata (AA), a putative autoimmune disease characterized by sudden hair loss, has remained obscure. It is not understood, how the characteristic inflammatory infiltrate that selectively attacks anagen hair follicles in AA is generated. We hypothesize that this reflects an unexplored form of autoimmunity, a cytotoxic T cell attack on rhythmically synthesized autoantigens normally sequestered by a lack or very low level of MHC class I (MHC I)-expression, and suggest the following mechanism of AA pathogenesis: Microtrauma, neurogenic inflammation, or microbial antigens cause a localized breakdown of MHC I-"negativity" in the proximal anagen hair bulb via proinflammatory cytokines. This exposes autoantigens derived from melanogenesis-related proteins (MRP-DP), which are only generated during anagen, and triggers two successive waves of autoimmune responses: CD8+ cytotoxic T cells initiate AA after recognizing MRP-DP abnormally presented by MHC I molecules on hair matrix melanocytes and/or keratinocytes; a secondary attack, carried by CD4+ T cells and antigen presenting cells, is then mounted against MHC class II--presented additional autoantigens exposed by damaged melanocytes and keratinocytes. The latter causes most of the follicular damage, and extrafollicular disease, and depends greatly on the immunogenetic background of affected individuals. This unifying hypothesis explains the clinical heterogeneity and all salient features of AA, and argues that only the unlikely coincidence of multiple predisposing events triggers AA. The suppression of MHC I--expression and synthesis of MRP in the hair bulb, and the "tolerization" of MRP-DP autoreactive CD8+ T cells may be promising strategies for treating AA.