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Genetic Autosomal Dominant Inheritance 1

Question

Vignette: A 7-year-old girl is brought to her pediatrician by her parents due to concerns about her height. She is significantly shorter than her peers and has shown slow growth since infancy. Her parents comment that she also has delayed puberty. Upon examination, the girl's body proportions are normal, but her nails are brittle, and her hair is sparse and thin. Her skin is dry and cool to touch. Lab tests indicate low levels of thyroid hormones. She has been diagnosed with autoimmune thyroiditis. The patient's mother is also short in stature and was also diagnosed with autoimmune thyroiditis. Which of the following genetic patterns is most likely responsible for the condition in this family?

Choices

A. Autosomal dominant

B. Autosomal recessive

C. X-linked dominant

D. X-linked recessive

E. Mitochondrial inheritance

Answer

A. Autosomal dominant

Explanation

The condition described in the vignette is most likely autoimmune polyendocrinopathy-candidiasis-ectodermal dystrophy (APECED) or Autoimmune Polyglandular Syndrome Type 1. APECED is an autosomal dominant disorder that results from mutations in the autoimmune regulator (AIRE) gene. This gene is involved in the development of immune tolerance and the prevention of autoimmune disease. The features of APECED include chronic mucocutaneous candidiasis, hypoparathyroidism, and Addison's disease. However, other endocrine glands can also be affected, including the thyroid gland, as in this case. The patient's height is likely affected by both her thyroid condition and her genetics. The fact that the mother also has the condition strongly suggests an autosomal dominant inheritance pattern. Autosomal dominant disorders often show a vertical pattern of inheritance in the pedigree, with affected persons present in each generation. Affected males and females can transmit the disorder with equal likelihood to their sons or daughters.