ABD Genodermatoses and Nevi 2

Question 1

Neurofibromatosis type 1 is caused by a mutation in which gene?

Accepted Answer

NF1 (neurofibromin)

Answer

NF1 results from loss-of-function mutations in the NF1 gene encoding neurofibromin, a RAS-GTPase-activating protein.

Question 2

Which diagnostic criterion requires at least six lesions greater than 5 mm (prepubertal) in neurofibromatosis type 1?

Accepted Answer

Café-au-lait macules

Answer

Six or more café-au-lait macules >5 mm prepubertal (>15 mm postpubertal) is a hallmark NIH diagnostic criterion for NF1.

Question 3

Ash-leaf macules (hypopigmented spots best seen with Wood lamp) are an early sign of which genodermatosis?

Accepted Answer

Tuberous sclerosis complex

Answer

Ash-leaf (lance-ovate) hypopigmented macules are one of the earliest cutaneous findings in tuberous sclerosis complex.

Question 4

The facial angiofibromas of tuberous sclerosis were historically misnamed as what?

Accepted Answer

Adenoma sebaceum

Answer

The angiofibromas of tuberous sclerosis were long called 'adenoma sebaceum,' a misnomer since they are not of sebaceous origin.

Question 5

A collagenous connective tissue nevus presenting as a leathery plaque over the lumbosacral area in tuberous sclerosis is called a:

Accepted Answer

Shagreen patch

Answer

The shagreen patch is a connective tissue nevus (collagenoma) classically located on the lower back in tuberous sclerosis.

American Board of Dermatology (ABD) Practice Test