Dementia is a chronic or progressive syndrome, characterized by impaired cognitive capacity beyond what could be considered a consequence of normal aging. It affects the memory, thinking process, orientation, comprehension, calculation, learning ability, language, and judgment; although awareness is usually unaffected. Alzheimer's disease (AD) is the most common form of dementia; symptoms include memory loss, difficulty solving problems, disorientation in time and space, among others. The disease was first described in 1906 at a conference in Tubingen, Germany by Alois Alzheimer. One hundred and ten years since its first documentation, many aspects of the pathophysiology of AD have been discovered and understood, however gaps of knowledge continue to exist. This literature review summarizes the main underlying neurobiological mechanisms in AD, including the theory with emphasis on amyloid peptide, cholinergic hypothesis, glutamatergic neurotransmission, the role of tau protein, and the involvement of oxidative stress and calcium.

Background It is estimated that 20% of the general population is sensitized to some kind of contact allergen. Contact dermatitis is one of the major occupational diseases worldwide. This disease has a higher prevalence in the female gender and is more frequently observed in the third or fourth decade of life. The main objective of this study was to describe the main sociodemographic and clinical characteristics of patients with contact dermatitis treated in the Allergy Unit of the San Juan De Dios Hospital – Caja Costarricense de Seguro Social. Methods Clinical records of contact dermatitis outpatients from a single hospital were analyzed, in a 4-year retrospective observational study. Results At the time of the patch testing, patients showed a mean age of 42.2 years. Disease frequency was higher in the female population (female/male ratio of 4.2:1) and in patients mostly dedicated to household workchores. Most patients presented several years of disease history, and the hands were the highest affected body part. Patch testing revealed that nickel sulfate, Cl+Me-Isothiazolinone (Kathon CG), and thimerosal were allergens regularly associated with contact dermatitis in the analyzed population. Conclusions To a great extent, sociodemographic and clinical characteristics identified in these patients resemble what is reported in other regions, including the Americas and worldwide. It is worth highlighting a high female proportion rate probably related to cultural aspects, a smaller percentage of irritant contact dermatitis that may be associated to institutional patient management, and a slight difference in the most common allergens when compared to other published studies.

Wilson's disease is an inherited disorder in which defective biliary excretion of copper leads to its accumulation, particularly in the liver and brain. Mutations in the ATP7B gene on chromosome 13 cause Wilson's disease. If left untreated it will cause liver failure, neurological damage, and will be life threatening. It is considered a rare disease afflicting approximately 1 in 30,000 persons worldwide, although this rate is similar in the different countries some places show higher incidence rates. Since Costa Rica reports the highest number of cases per population, essential public health initiatives that promote wellbeing, prevent disease complications, and prolong life among the affected population have been carried out during the last decades. The most recent lead in this matter is the conformation of the Costa Rica's National Alliance for Wilson's disease whose main objective is to provide practical, operational, timely and relevant guidance to patients, families, and healthcare professionals in the region for early diagnosis and treatment. The development and implementation of the National Alliance for Wilson's disease activities is crucial because it will reaffirm that early intervention and appropriate treatment, will reduce if not eliminate the burden of Wilson's disease.

Considering the etiology of multiple sclerosis (MS) is still unknown, experimental models resembling specific aspects of this immune‐mediated demyelinating human disease have been developed to increase the understanding of processes related to pathogenesis, disease evolution, evaluation of therapeutic interventions, and demyelination and remyelination mechanisms. Based on the nature of the investigation, biological models may include in vitro, in vivo, and ex vivo assessments. Even though these approaches have disclosed valuable information, every disease animal model has limitations and can only replicate specific features of MS. In vitro and ex vivo models generally do not reflect what occurs in the organism, and in vivo animal models are more likely used; nevertheless, they are able to reproduce only certain stages of the disease. In vivo MS disease animal models in mammals include: experimental autoimmune encephalomyelitis, viral encephalomyelitis, and induced demyelination. This review examines and describes the most common biological disease animal models for the study of MS, their specific characteristics and limitations.