A 32-year-old woman comes to the office due to worry that she will go bald. Her father had a receding hairline with apical baldness beginning at age 20 and was completely bald by age 35. The patient's paternal grandmother and multiple other relatives on her paternal side also had early-onset baldness, but her father's siblings and the maternal side of her family have had no problems with unusual hair loss. Physical examination shows mild thinning of hair at the temporal areas, with an otherwise normal hairline, thickness, and coloration. There is no excess hair growth on her face or trunk, and she has a normal female pattern of pubic hair growth. Palpation of the thyroid is normal. Which of the following is the most likely inheritance pattern of the hair loss in this patient's family?

Question

A 32-year-old woman comes to the office due to worry that she will go bald.  Her father had a receding hairline with apical baldness beginning at age 20 and was completely bald by age 35.  The patient's paternal grandmother and multiple other relatives on her paternal side also had early-onset baldness, but her father's siblings and the maternal side of her family have had no problems with unusual hair loss.  Physical examination shows mild thinning of hair at the temporal areas, with an otherwise normal hairline, thickness, and coloration.  There is no excess hair growth on her face or trunk, and she has a normal female pattern of pubic hair growth.  Palpation of the thyroid is normal.  Which of the following is the most likely inheritance pattern of the hair loss in this patient's family?

Quizplus · Accepted Answer

11ec160b_3757_44d0_9249_51da06c0e975_MD0001_00 The most common type of hair loss in males and females is androgenetic alopecia (male pattern baldness). As the name implies, the hair loss is driven by both hormonal (eg, circulating androgens) and genetic factors. The hair loss occurs primarily at the temporal areas and vertex and progresses through life. The pattern and severity vary between males and females. Androgenetic alopecia demonstrates polygenic inheritance with variable expressivity. Key sites of genetic influence have been identified on the short arm of chromosome 20, and also on the X and possibly Y chromosomes. Therefore, some of the genetic factors may be transmitted with X-linked recessive inheritance (eg, gene variations in the androgen receptor), whereas others will show autosomal dominant inheritance (Choice A). (Choice B) Autosomal recessive inheritance classically shows disease development in 25% of offspring from 2 asymptomatic carrier parents. In most cases, conditions with autosomal recessive inheritance will not be seen in consecutive generations. (Choice C) Conditions passed through mitochondrial inheritance are transmitted only by the mother, and all of her offspring are affected. Conditions transmitted by mitochondrial inheritance include a number of uncommon neuromuscular disorders. (Choice E) By definition, sporadic cases do not follow an inheritance pattern. Sporadic cases occur haphazardly among unrelated members of a population over time. For example, there may be a spontaneous gene mutation that causes a sporadic disorder in an individual with no family history of the disease. Educational objective: Androgenetic alopecia is the most common cause of hair loss in both males and females. The pattern and severity of the baldness depend on both hormonal (circulating androgens) and genetic factors and vary between males and females. The condition is polygenic with variable expressivity. __________ References: Genetic variation in the human androgen receptor gene is the major determinant of common early-onset androgenetic alopecia. (http://www.ncbi.nlm.nih.gov/pubmed/15902657) Male-pattern baldness susceptibility locus at 20p11. (http://www.ncbi.nlm.nih.gov/pubmed/18849991)

A 32-Year-Old Woman Comes to the Office Due to Worry