The purpose of this study was to characterize the clinical and serological features of a large cohort of patients with antinuclear antibody (ANA) positive undifferentiated connective tissue disease (UCTD). Consecutive patients with UCTD, followed up at the Rheumatology Clinic of the participating centers, were included. Data from these patients were obtained by clinical evaluation and chart review. All patients were diagnosed as having UCTD on basis of the following criteria: positive ANA plus at least one clinical feature of connective tissue disease, but not fulfilling classification criteria for any differentiated connective tissue disease. One hundred eighty-four patients were studied (female patients-94.5%; mean age at time of evaluation-47 years). The most prevalent manifestations were arthralgia (66%), arthritis (32%), Raynaud's phenomenon (30%), sicca symptoms (30%), and leukopenia (19%). The prevalence of ANA was 100%, anti-SSA 20%, antidsDNA 14%, and anti-SSB 7%. Patients with anti-dsDNA/ anti-Sm, anticentromere/anti-Scl70, or anti-SSA/anti-SSB antibodies more frequently presented a set of manifestations close to systemic lupus erythematosus (SLE), systemic sclerosis, or Sjögren syndrome, respectively. We analyze a large cohort of UCTD. Seventy-two percent of these UCTD patients present lupus-, scleroderma-, or Sjögren-like features but do not fulfill classification criteria and mostly present a mild disease.

Since its launch in 2009, bitcoin has thrived, attracting the attention of investors, regulators, academia, and the public in general. Its price dynamics, characterized by extreme volatility, severe jumps, and impressive long-term appreciation, suggest that bitcoin is a new digital asset. This study presents a comprehensive overview of the fractality of bitcoin in a high-frequency framework, namely by applying Multifractal Detrended Fluctuation Analysis (MF-DFA) and a Multifractal Regime Detecting Method (MRDM) to Bitstamp 1 min bitcoin returns from January 2013 to July 2020. The results suggest that bitcoin is multifractal, with smaller and larger fluctuations being persistent and anti-persistent, respectively. Multifractality comes from significant long-range correlations, which cast some doubts on the informational efficiency at this frequency, but mainly comes from fat-tails, which highlights the significant risks undertaken by investors in this market. Our most important result is that the degree and richness of multifractality is time-varying and increased after 2017, when volumes and prices experienced an explosive behaviour. This complexity puts into perspective the duality of bitcoin: while it is characterized by long-run attractiveness and increasing valuation, it also has a high short-run instability. Hence, this study provides some empirical evidence supporting the relationship between these two observable features.