Trisomy 13 or Patau syndrome (PS) is a chromosomal disorder characterized by a 
well known presentation of multiple congenital anomalies. Our objective was to 
determine the clinical features and prognosis observed in a sample of patients 
with PS. The series was composed of patients with diagnosis of PS consecutively 
evaluated by a Clinical Genetics Service from a reference hospital of southern 
Brazil, in the period between 1975 and 2012. Statistical analysis was performed 
using PEPI program (version 4.0), with two-tailed Fisher's exact test for 
comparison of frequencies (P<0.05). The sample consisted of 30 patients, 60% 
male, median age at first evaluation of 9 days. Full trisomy of chromosome 13 
was the main cytogenetic alteration (73%). The major clinical findings included: 
cryptorchidism (78%), abnormal auricles (77%), congenital heart defects (76%), 
polydactyly (63%), microphthalmia (60%) and micrognathia (50%). Four patients 
(13%) simultaneously had micro/anophthalmia, oral clefts and polydactyly. Some 
findings were only observed in our sample and included, among others, 
preauricular tags (10%), duplication of the hallux (3%) and spots following the 
lines of Blaschko (3%). Mosaicism (20% of cases) had a statistically significant 
association only with absence of cryptorchidism. The median of survival was 26 
days. Patients with and without mosaicism had similar median of survival. Our 
findings, in agreement with the literature, show that the anomalies in patients 
with PS can be quite variable, sometimes even atypical. There is no 
pathognomonic finding, which may make the early identification of these patients 
challenging.