Dear Editor,

Psoriasis is a complex, multifactorial, chronic inflammatory disease involving the skin, characterized by keratinocytes hyper-proliferation and vascular alteration, presenting clinical variability; it may or may not be associated with inflammation of the joints.1

Psoriasis prevalence studies are more numerous than incidence studies in the literature, probably because notification of the disease is not mandatory.2 Therefore, this study determined the prevalence of psoriasis in a family in Goiás State, Brazil, according to the phenotype defined through clinical diagnosis at a private clinic and a public hospital. Data were collected between 2003 and 2016. Patients provided informed consent for use of their data for research and publication in scientific journals.

As shown in the pedigree chart of 156 members of this family from Goiás, 37 individuals presented vulgar, pustular or arthropathic psoriasis, representing a prevalence of approximately 23%. Of these patients with psoriasis, 20 (54%) were male, and 17 (46%) were female (Figure 1). Non-psoriatic clinical manifestations included severe and extensive follicular hyperkeratosis throughout the body, which was diagnosed in 1 patient whose father had severe psoriasis. Eleven individuals presented nonspecific skin lesions that could progress to psoriasis, and 3 of these individuals subsequently had a clinical diagnosis of psoriasis confirmed.

Figure 1.

Psoriasis pedigree chart of a family from Goiás State, Brazil

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This study found that men were more affected by the disease than women, but the values did not present significant difference. The majority of studies have also reported a higher prevalence of the disease in males and adults, although psoriasis may occur equally in both genders and at any age.2

Prevalence data found in this study were higher than the values reported in the Central-West region and in the Brazilian capitals. Recently, Romiti et al. (2017) reported the psoriasis prevalence in Brazil.3 According to the study, the prevalence of the disease varies between 1.10% and 1.51%, showing that, within the Brazilian capitals, differences exist between geographical regions and between age groups. Another study reported a psoriasis prevalence of 2.15% in the São Paulo State population.4

Monogenic or Mendelian disorders present a classic Mendelian segregation pattern, i.e., fixed proportions among progeny. The pattern is characterized by a recognizable inheritance and by the presence of a phenotype highly correlated with a single gene at the causal locus of the disease. The multifactorial inheritance pattern, however, results from complex interactions of various genetic and environmental factors.5

The etiopathogenesis of psoriasis is very complex and not yet fully known. It is considered an immuno-mediated genetic disease, involving interaction with the environment and exhibiting a multifactorial inheritance pattern.1,5 As seen in the pedigree chart shown here, psoriasis does not present Mendelian inheritance, but is instead multifactorial.

The present study showed a high prevalence of psoriasis in a family from the Goiás State, Brazil, finding a multifactorial pattern of inheritance, with more men than women being affected by the disease. Future studies may be conducted to analyze and determine disease-related mutations in this family, relating to the clinical phenotype.