The severity and localization of disease presentation is dependent on the timing and stage of tooth development in which the defective enamel formation occurred. Hereditary causes of enamel hypoplasia include:

Primary abnormalities in enamel development, such as amelogenesis imperfecta
Certain dermatological conditions, such as Ehlers-Danlos syndrome
Other complex hereditary conditions such as Usher syndrome, Seckel syndrome, Treacher-Collins syndrome, Heimler syndrome & Ellis-Van Creveld syndromeEnvironmental causes of enamel hypoplasia include:

Nutritional deficits, such as Vitamin D, iron or calcium deficiency
Birth injury or preterm birth
Smoking during pregnancy
Trauma
Radiation
Certain infections (e.g. congenital syphilis, cytomegalovirus, congenital rubella)
Certain diseases (such as undiagnosed and untreated celiac disease, chicken pox, congenital syphilis)
High fever
Hypoxia (i.e. from severe cardiac defect)
Excessive fluoride exposure (dental fluorosis)
Tetracycline
Vitamin A, C, or D deficiency

Clinical relevance
Enamel hypoplasia is a risk factor for dental caries in children including early childhood caries (ECC), which continues to be a burden for many children. This association has been identified as significant and independent, and is believed that the formation of pits and missing enamel provides a suitable local environment for adhesion and colonization of cariogenic bacteria. Historically, enamel hypoplasia has been under-appreciated as a risk factor for ECC. Developmental defects in enamel that affect tooth appearance in the esthetic zone (i.e. upper front teeth) may cause individuals to experience social embarrassment or anxiety regarding the appearance of their teeth. Guidelines for Treatment of Enamel Hypoplasia
Dental sealants may be indicated for the prevention of caries in hypoplastic pit & fissure systems.
Christianson syndrome is an X linked syndrome associated with intellectual disability, microcephaly, seizures, ataxia and absent speech. Presentation
Onset of symptoms is normally within the first year of life with truncal ataxia and seizures. The head is small (microcephaly). Common facial abnormalities include:
Long narrow face
Prominent nose
Prominent jaw
Large ears
Open mouth
Thick eyebrowsOther common features include:
Uncontrolled drooling
Abnormal eye movementsThe associated intellectual disability is usually in the profound range. Those affected often have a happy demeanor with frequent smiling and spontaneous laughter. Genetics
This condition is caused by mutations in the SLC9A6 gene. This gene is located on the long arm of the X chromosome (Xq26.3). The gene encodes a sodium/hydrogen exchanger located in the endosomes. Mutations in this gene cause a rise in the pH of the endosomes.How this causes the clinical features is not known presently. The inheritance of this condition is X-linked dominant. Diagnosis
The diagnosis may be suspected on clinical grounds.It is made by sequencing the SLC9A6 gene. Differential diagnosis
Angelman syndrome
Spinocerebellar ataxia type 29

Management
There is presently no curative treatment. Management is supportive. Epidemiology
The prevalence is not known but this is considered to be a rare disease. History
This condition was first described in 1999. The causative mutation was discovered in 2008. == References ==