What condition is characterized by the absence of hair and missing teeth?

Ectodermal dysplasia is a genetic condition that affects the development of the skin, hair, teeth, and sweat glands due to abnormalities in the ectoderm, the outermost layer of the embryo. Individuals with ectodermal dysplasia often experience a variety of symptoms, including sparse or absent hair (hypotrichosis) and a reduced number of teeth (oligodontia) or missing teeth altogether. This condition can also lead to other issues such as heat intolerance and dry skin, as sweat gland development may also be impaired.

The other conditions mentioned do not typically present with both absent hair and missing teeth. Pernicious anemia primarily affects the body's ability to absorb vitamin B12, leading to anemia but not hair or teeth defects. Hemolytic anemia involves the destruction of red blood cells and is unrelated to hair or dental anomalies. Hereditary telangiectasia involves blood vessel abnormalities and has no association with hair or tooth development issues. Therefore, ectodermal dysplasia is the condition that aligns with the symptoms described in the question.