The formation of human enamel is highly regulated at the molecular level and involves thousands of genes. Requisites for development of this highly mineralized tissue include cell differentiation; production of a unique extracellular matrix; processing of the extracellular matrix; altering of cell function during different stages of enamel formation; cell movement and attachment; regulation of ion and protein movement; and regulation of hydration, pH, and other conditions of the microenvironment, to name just a few. Not surprising, there is a plethora of hereditary conditions with an enamel phenotype. The objective of this review was to identify the hereditary conditions listed on Online Mendelian Inheritance in Man (OMIM) that have an associated enamel phenotype and whether a causative gene has been identified. The OMIM database was searched with the terms amelogenesis, enamel, dental, and tooth, and all results were screened by 2 individuals to determine if an enamel phenotype was identified. Gene and gene product function was reviewed on OMIM and from publications identified in PubMed. The search strategy revealed 91 conditions listed in OMIM as having an enamel phenotype, and of those, 71 have a known molecular etiology or linked genetic loci. The purported protein function of those conditions with a known genetic basis included enzymes, regulatory proteins, extracellular matrix proteins, transcription factors, and transmembrane proteins. The most common enamel phenotype was a deficient amount of enamel, or enamel hypoplasia, with hypomineralization defects being reported less frequently. Knowing these molecular defects allows an initial cataloging of molecular pathways that lead to hereditary enamel defects in humans. This knowledge provides insight into the diverse molecular pathways involved in enamel formation and can be useful when searching for the genetic etiology of hereditary conditions that involve enamel.

Hereditary conditions are traditionally classified based either on physical/physiological attributes or using the names of the individuals credited with identifying the condition. For the 170 plus conditions classified as ectodermal dysplasias (EDs), both of these nosological systems are used, at times interchangeably. Over the past decade our knowledge of the human genome and the molecular basis of the EDs have greatly expanded providing the impetus to consider alternative classification systems. The incorporation of the molecular basis of hereditary conditions adds important information allowing effective transfer of objective genetic information that can be lacking from traditional classification systems. Molecular information can be added to the nosological system for the EDs through a hierarchical- and domain-based approach that encompasses the condition's name, mode of inheritance, molecular pathway affected, and specific molecular change. As new molecular information becomes available it can be effectively incorporated using this classification approach. Integrating molecular information into the ED classification system, while retaining well-recognized traditional syndrome names, facilitates communication at and between different groups of people including patients, families, health care providers, and researchers.

Portuguese man-of-war stings occur frequently at North American beaches. Most produce only local pain and pruritis. A 4-year-old girl who developed a hemolytic reaction and acute renal failure following a severe sting is described. As neither sequela has been previously reported, it is speculated that either the large dose of venom or chance intravenous inoculation may have been responsible. Evidence of hemolysis should be sought in small children with extensive Portuguese man-of-war stings.