Introdução: Penfigoide bolhoso (PB) resulta da produção de autoanticorpos contra proteínas hemidesmossomais BP (Bullous Pemphigoid) 180 e/ou 230, acomete os idosos, e está associado com doenças neurológicas (DN), especialmente com a demência (DEM). BP180/230 foram identificadas no Sistema Nervoso Central (SNC), aventando-se possível mimetismo antigênico entre moléculas da pele e do SNC. O fator neurotrófico derivado do cérebro (BDNF) participa da neurogênese, sinaptogênese e sobrevivência neuronal, e a sua diminuição sérica tem sido relacionada com DN. Objetivo: Quantificar o peptídeo BDNF e os anticorpos anti-BP180/230 na relação PB com DEM. Material e Métodos: Em estudo comparativo, 50 pacientes com PB, 50 com demência e 50 controles foram avaliados. A detecção dos anticorpos anti-BP180/P230 e do peptídeo BDNF foi determinada por ensaios ELISA. Imunofluorescência indireta (IFI) foi conduzida nas amostras de soro dos pacientes do grupo DEM e dos controles que apresentaram positividade para anti-BP180/230. Resultados: No grupo PB, a frequência de DN foi de 26%: DEM 16%, acidente vascular cerebral 6%, e epilepsia 4% - 5/8 (63%) pacientes apresentaram demência vascular e 3/8 (38%) demência por doença de Alzheimer. Positividade para anti-BP180/230 foi observada no grupo PB (74% e 40%, respectivamente), no grupo DEM (10% e 10%) e nos controles (14% e 0%). No grupo DEM, em 2/10 pacientes que apresentaram positividade para antiBP180/230, a IFI evidenciou depósito de IgG e C3 no lado epidérmico da clivagem, configurando quadro subclínico de PB. A mediana do BDNF resultou menor no grupo DEM (25,41 pg/ml) comparado aos controles (38,21 pg/mL), e o grupo PB apresentou os menores valores de BDNF (16,88 pg/mL). Não houve correlação dos títulos de anticorpos antiPB180/230 com a concentração do peptídeo BDNF no grupo PB. Os pacientes do grupo DEM foram alocados de acordo com a escala de demência - CDR1, CDR2 e CDR3; a mediana de BDNF do subgrupo CDR3 (23,37 pg/mL) foi inferior ao CDR1 (30,17 pg/ mL). Não houve diferença na concentração do BDNF segundo o tipo de demência. O grupo PB, quando estratificado em - com DEM, outras DN e sem DN, aqueles com associação com DEM apresentaram menores níveis de BDNF (9,1 pg/mL), comparados ao grupo sem DN e ao subgrupo CDR3 do grupo DEM. Conclusão: Marcadores para PB não são úteis para o diagnóstico de DEM. Valores sorológicos baixos de BDNF no grupo PB podem sugerir associação com DEM. BDNF pode ser utilizado como biomarcador de gravidade da DEM.

Introduction: Bullous pemphigoid (BP) is characterized by autoantibodies against the hemidesmossomal proteins BP180 and/or BP230, affects the elderly people and has been strongly associated with neurological disorders (ND), especially dementia. A possible antigenic mimicry hypothesis between the skin and the nervous system molecules is strong reasonable because BP peptides have also been identified in the central nervous system (CNS). Brain-derived neurotrophic factor (BDNF) plays a role in the synaptogenesis, neurogenesis, and neuronal survival, and some studies have been correlated the decreased serum BDNF levels with ND. The aim of this study was to quantify the BDNF peptide and the anti-BP180 and anti-BP230 antibodies in the BP and DEM relationship. Methods: AntiBP180/230 and BDNF quantification were analyzed in three groups: 50 patients with BP, 50 patients with dementia and 50 elderly individuals comprised a case-control study. Serum IgG anti-180/230, and the BDNF peptide were evaluated by using ELISA commercial kits; and immunofluorescence allied to salt split skin technique (SSS) was conducted in serum samples from patients of the dementia group and from controls who showed positive anti-BP180/230. Results: In BP group, 26% were associated with ND, and dementia was the most frequent (16%), followed by stroke (6%) and epilepsy (4%) - 5/8 (63%) patients showed vascular dementia and 3/8 (38%) patients presented dementia due to Alzheimer's disease. AntiBP180/230 positivity was observed in BP group (74%, 40%, respectively), in dementia group (10%, 10%) and in controls (14%, 0%). In 2/10 patients of the dementia group with positive anti-BP180/230, IIF showed IgG and C3 deposition in the epidermal side of cleavage, configuring a subclinical BP dermatosis. The medians of BDNF resulted lower in the patients of the dementia group (25.41 pg/mL) compared with controls (38.21 pg/mL), and the BP group presented the lowest BDNF values (16.88 pg/mL). There was no correlation between the anti-BP180/230 antibodies titres and the BDNF levels in BP group. There was no difference of BDNF levels accordingly with the clinical type of dementia in the dementia group. Patients of the dementia group were sub grouped accordingly with the clinical dementia severity - CDR1, CDR2 and CDR3 - being the median of BDNF in CDR3 (23.37 pg/mL) lower than in CDR1 (30.17 pg/mL) subgroup. BP group had lower levels of BDNF compared to CDR3 subgroup. BP patients when stratified with dementia, other ND and without ND, those with association with dementia presented the lowest levels of BDNF (9.1 pg/mL) compared to the PB patients without DN and to the CDR3 subgroup. Conclusion: BP biomarkers are not useful for the diagnosis of dementia. Low BDNF levels seen in BP patients may suggest an association with dementia. BDNF may be used as a biomarker of severity of dementia.