Background/Objectives: Genodermatoses are genetic conditions with clinical symptoms manifesting in the skin and adjoining tissues, individually rare but comprising a large and heterogeneous group of disorders that represents 15% of genetic diseases. This article discusses the results of individuals with genodermatoses from a reference center for rare diseases studied through whole genome sequencing conducted by the Brazilian Rare Genomes Project between 2021 and 2023. Methods: A retrospective case series with data comprising sex, age at first assessment in the hospital, family history, clinical findings, and molecular results. Results: Excluding neurofibromatosis type 1, Ehlers–Danlos syndrome and RASopathies are discussed elsewhere. Diagnoses in this work comprised ectodermal dysplasias (n = 6), ichthyosis (n = 4), albinism (n = 4), tuberous sclerosis complex (n = 4), and incontinentia pigmenti (n = 3), in addition to 11 others with individual rare conditions. The sex ratio was 17:16 (M:F), consanguinity was present in 6/33 (18%), and the age at the first evaluation ranged from neonatal to 26 years (median 13.65 years). Negative results were 3/33 (9%), novel variants were 17/41 (41.4%), and 7/30 (23%) presented initially with a double molecular diagnosis, three confirming composed phenotypes. Conclusions: Besides reporting 17 novel variants in 14 genes (BLM, CACNA1B, EDA, ELN, ENG, ERC6, EVC2, PNPLA1, PITCH1, PORCN, SIN3A, TP63, TYR, and WNT10B), the study also identified three atypical clinical presentations due to dual diagnoses, and the c.454C>T variant in the SDR9C7 gene, previously reported only in dogs, was, for the first time, confirmed as causative for ichthyosis in humans.

Pigmentary mosaicism of Ito (PMI) is a skin abnormality often characterized by hypopigmentation of skin, following, in most cases, the Blaschko lines, usually associated with extracutaneous abnormalities, especially abnormalities of the central nervous system (CNS). It is suggested that this pattern arises from the presence and migration of two cell lineages in the ectoderm layer during the embryonic period and embryonic cell migration, with different gene expression profiles associated with pigmentation. Several types of chromosomal aberrations, with or without mosaicism, have been associated with this disorder. This study comprised clinical description and cytogenetic analysis of a child with PMI. The G-banded karyotype analysis revealed a supernumerary marker chromosome in 76% of the analyzed metaphases from peripheral blood lymphocytes. Array genomic hybridization analysis showed a copy number gain between 3q26.32-3q29, of approximately 20.5 Mb. Karyotype was defined as 47,XX,+mar[38]/46,XX[12].arr 3q26.32-3q29(177,682,859- 198,043,720)x4 dn. Genes mapped in the overlapping region among this patient and three other cases described prior to this study were listed and their possible involvement on PMI pathogenesis is discussed.