Online Mendelian Inheritance in Man (OMIM®): Victor McKusick's magnum opus

Victor McKusick's many contributions to medicine are legendary, but his magnum opus is Mendelian Inheritance in Man (MIM), his catalog of Mendelian phenotypes and their associated genes. The catalog, originally published in 1966 in book form, became available on the internet as Online Mendelian Inheritance in Man (OMIM®) in 1987. The first of 12 editions of MIM included 1486 entries; this number has increased to over 25,000 entries in OMIM as of April 2021, which demonstrates the growth of knowledge about Mendelian phenotypes and their genes through the years. OMIM now has over 20,000 unique users a day, including users from every country in the world. Many of the early decisions made by McKusick, such as to maintain MIM data in a computer‐readable format, to separate phenotype entries from those for genes, and to give phenotypes and genes MIM numbers, have proved essential to the long‐term utility and flexibility of his catalog. Based on his extensive knowledge of genetics and vision of its future in the field of medicine, he developed a framework for the capture and summary of information from the published literature on phenotypes and their associated genes; this catalog continues to serve as an indispensable resource to the genetics community.

Novel and recurrent mutations in the TAT gene in Tunisian families affected with Richner-Hanhart syndrome

Tyrosinemia type II, also designated as oculocutaneous tyrosinemia or Richner-Hanhart syndrome (RHS), is a very rare autosomal recessive disorder. In the present study, we report clinical features and molecular genetic investigation of the tyrosine aminotransferase (TAT) gene in two young patients, both born to consanguineous unions between first-degree cousins. These two unrelated families originated from Northern and Southern Tunisia. The clinical diagnosis was based on the observation of several complications related to Richner-Hanhart syndrome: recurrent eye redness, tearing and burning pain, photophobia, bilateral pseudodendritic keratitis, an erythematous and painful focal palmo-plantar hyperkeratosis and a mild delay of mental development. The diagnosis was confirmed by biochemical analysis. Sequencing of the TAT gene revealed the presence of a previously reported missense mutation (c.452G>A, p.Cys151Tyr) in a Tunisian family, and a novel G duplication (c.869dupG, p.Trp291Leufs 6). Early diagnosis of RHS and protein-restricted diet are crucial to reduce the risk and the severity of long-term complications of hypertyrosinemia such as intellectual disability.

Trimethylaminuria (fish odor syndrome): genotype characterization among Portuguese patients

Trimethylaminuria (TMAu) or "fish odor syndrome" is a metabolic disorder characterized by the inability to convert malodorous dietarily-derived trimethylamine (TMA) to odorless TMA N-oxide by the flavin-containing monooxygenase 3 (FMO3). Affected individuals unable to complete this reaction exude a "fishy" body odor due to the secretion of TMA in their corporal fluids leading to a variety of psychosocial problems. Interindividual variability in the expression of FMO3 gene may affect drug and foreign chemical metabolism in the liver and other tissues. Therefore, it is important to screen for common TMAu mutations but also extend the search to other genetic variants in order to correlate genotype and disease-associated phenotypes. In this study, 25 Portuguese patients with phenotype suggestive of TMAu were evaluated for molecular screening of the FMO3 gene. Herein, we found 16 variants in the FMO3 coding region, some of which had not been previously documented (Gly38Trp, Asp232Val, Thr307Pro, Ser310Leu). Whenever common variants (Glu158Lys, Glu308Gly) were considered in combination a distinct pattern between the control population and patients was observed, mainly in what concerns the presence of Lys158 and Gly308 in homozygous state. Further studies are necessary to clarify the pathogenicity of novel variants identified in this study, as well as the effect of the common single nucleotide polymorphisms, which may play an important role in disease presentation and/or protective mechanism to xenobiotics drugs or environment.