Hypomaturation Amelogenesis Imperfecta

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Amelogenesis imperfecta (AI) is a heterogeneous genetic disorder which affects the dental enamel. It can have an autosomal dominant, autosomal recessive or X-linked pattern. The authors describe a case of a family with hypomaturation X-linked AI and discuss the clinical and histopathological aspects of this disorder. 
Amelogenesis imperfecta (AI) is a group of hereditary defects of the enamel not associated with any other generalized defect. The prevalence of this condition is 1:718 to 1:14000, depending on the population studied (Seow, 1993). Its genetic inheritance pattern can be autosomal dominant, autosomal recessive or X-linked. It is an exclusively ectodermal disorder, because the mesodermic components of the teeth are not altered (Shafer et al., 1987). Its etiology is related to the alteration of genes involved in the process of formation and maturation of the enamel (Seow, 1993).
The genetic origin of the autosomal forms is still unknown, although the cause of X-linked amelogenesis imperfecta is definitely related to defects in the amelogenin gene, which is the principal protein related to the formation of human dental enamel (Line and Trevilato, 1996). The human amelogenin gene is in the distal region of the p 22.1 ® p 22.3 short arm of the X chromosome and in the pericentromeric region of the Y chromosome. The determination of the human amelogenin gene in the p 22 region of the X chromosome, together with the discovery of the locus of AI in the Xp22.2 region, support the association of this gene with the different AI phenotypes that have inheritance linked to this chromosome (Lau et al., 1990).
This genetic alteration can be divided into 3 main types: hypoplastic, hypocalcified and hypomaturation, according to the clinical characteristics of the enamel, which reflect the stage of formation at which the enamel was affected. Each type can be subdivided into subtypes depending on the mode of inheritance, as well as on the clinical and radiographic aspect of the enamel defect, although in some cases characteristics overlap, making classification difficult (Seow, 1995).
The hypoplastic types are characterized by a deficiency in the quantity of enamel, which can be expressed clinically through a fine enamel, or with grooves and pits on its surface. The hypocalcified types show an enamel that has low mineralization, manifested clinically by a pigmented, softened and easily detachable enamel. The hypomaturation types are associated with anomalies of the maturation stage during the formation of the enamel, resulting in an opaque and porous enamel (Shafer et al., 1987; Seow, 1993).
This article describes a case of a family with hypomaturation amelogenesis imperfecta, whose transmission pattern suggests X-linked inheritance.

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From the radiograph one can note that all of the teeth have the defect of having little or no enamel.  The pulp chambers and canals appear within normal limits. Her deciduous teeth were affected.  Depending on the type of genetic inheritance, other immediate family members may not have the condition but a family pedigree would indicate it in other generations.

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Other Names: 
Hypomaturation Amelogenesis Imperfecta

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