Pediatric Dentistry · patient case question
All of the following are true of hypohidrotic ectodermal dysplasia EXCEPT:
Patient case: A father who says his son has no teeth
demo: 6-year-old male, accompanied by his father
chief: The father is worried that his son still has almost no teeth.
history: Born at term. The father reports the boy overheats badly in summer and has to be cooled with wet towels; he rarely seems to sweat. He has never been seen by a specialist.
meds: None.
findings: Sparse fine scalp hair, prominent periorbital wrinkling with darkening around the eyes, frontal bossing, a depressed nasal bridge and everted lips. The skin is dry and scaly. Only two conical teeth are present in each arch.
Show answer and explanation
Correct answer: C. It follows a Y-linked pattern of inheritance
- A. This is true. Skin glands and hair follicles are ectodermal, so the skin is dry and the hair sparse, fine and light in colour.
- B. This is true. Periorbital wrinkling with hyperpigmentation, frontal bossing, a depressed nasal bridge and everted lips give the recognisable facies.
- C. Correct, and this is the exception. The classic form is X-linked recessive, caused by mutations in the EDA gene at Xq12-13. It is not Y-linked. A Y-linked condition would pass only father to son and would never appear in females, which is not the pattern seen.
- D. This is true and follows from X-linked recessive inheritance. Males, being hemizygous, are fully affected, while carrier females show milder patchy signs such as a few missing or conical teeth and reduced sweating in a mosaic distribution.
Note: An autosomal recessive form also exists and affects both sexes equally, but the X-linked form is the one tested.
Practice Pediatric Dentistry questions Pediatric Dentistry study notes