A 32yo female with axillary freckles and café au lait spots wants to know the chances of her child also having similar condition.
a. 1:2
b. 1:4
c. No genetic link
d. 1:16
e. Depends on the genetic make up of the partner
answer: E
It is very rare to have 2 autosomal dominant parents for a disease but technically we cannot say for sure til we know the status of the father:
if both parents have the disease:
Nn + Nn
NN Nn nN nn (75% chance of having it)
if only the mother has it
Nn + nn
Nn Nn nn nn (50% chance)
NEUROFIBROMATOSIS TYPE I
• autosomal dominant
• also known as von Recklinghausen disease
• incidence 1:3,000, mutation in NF1 gene on 17q11.2 (codes for neurofibromin protein)
• learning disorders, abnormal speech development, and seizures are common
• diagnosis of NF-1 requires 2 or more of
≥6 café-au-lait spots (>5 mm if prepubertal, >1.5 cm if postpubertal)
≥2 neurofibromas of any type or one plexiform neurofibroma
≥2 Lisch nodules (hamartomas of the iris)
optic glioma
freckling in the axillary or inguinal region
a distinctive bony lesion (e.g. sphenoid dysplasia, cortical thinning of long bones)
a first degree relative with confirmed NF-1
NEUROFIBROMATOSIS TYPE II
• autosomal dominant
• incidence 1:33,000
• characterized by predisposition to form intracranial, spinal tumors
• diagnosed when either bilateral vestibular schwannomas are found, or a first-degree relative with NF-2 and either a neurofibroma, meningioma, glioma, or schwannoma is found
• also associated with posterior subcapsular cataracts
• treatment consists of monitoring for tumor development and surgery