Rapidly Progressive Dementia: Prevalence and Causes in a Neurologic Unit of a Tertiary Hospital in Brazil.

BACKGROUND: Rapidly progressive dementia (RPD) is usually associated with Creutzfeldt-Jakob disease, a fatal condition. Current advances in the understanding of immune-mediated diseases allow the diagnosis of previously unrecognized treatable RPDs. OBJECTIVE OF THE STUDY: The objective of the study was to describe the prevalence and causes of RPD in a neurology service, identifying potentially reversible causes. METHODS: We carried out a cross-sectional evaluation of all patients admitted to the neurology unit of a tertiary hospital in Brazil between March 2012 and February 2015. We included patients who had progressed to moderate or severe dementia within a few months or up to 2 years at the time of hospitalization, and used multivariable logistic regression analysis to identify factors associated with a favorable outcome. RESULTS: We identified 61 RPD (3.7%) cases among 1648 inpatients. Mean RPD patients' age was 48 years, and median time to progression was 6.4 months. Immune-mediated diseases represented the most commonly observed disease group in this series (45.9% of cases). Creutzfeldt-Jakob disease (11.5%) and nonprion neurodegenerative diseases (8.2%) were less common in this series. Outcome was favorable in 36/61 (59.0%) RPD cases and in 28/31 (89.3%) of immune-mediated cases. Favorable outcome was associated with shorter time from symptom onset to diagnosis and abnormal cerebrospinal fluid findings. CONCLUSIONS: Immune-mediated diseases were the most common cause of RPD in this series. Timely evaluation and diagnosis along with institution of appropriate therapy are required in RPD, especially in view of potentially reversible causes.

Fragile X-associated tremor/ataxia syndrome: intrafamilial variability and the size of the FMR1 premutation CGG repeat.

Fragile X-associated tremor/ataxia syndrome (FXTAS) is a neurological progressive disorder associated with the FMR1 gene premutation. We report on variable presentation of findings associated with FXTAS in 3 brothers aged 68, 74, and 73 years, carrying premutation alleles of (CGG)(123,) (CGG)(109), and (CGG)(91) triplets, respectively. Based on previously proposed diagnostic criteria for the syndrome, clinical and radiological data allowed establishing a "definite" diagnosis of FXTAS in the two carriers of the longest (CGG)(n). The carrier of the (CGG)(91) allele, although presenting a major radiological sign of the syndrome (symmetrical white-matter lesions in the middle cerebellar peduncles), did not have any significant neurological manifestation at 73 years of age.