Delayed development with light hair
Author:
Pediatric Oncall
Question
A 2 years old boy born of non-consanguineous marriage presented with cough and fever for 7 days. There is no history of contact with TB. He also has delayed milestones and is not able to sit, roll over, hold head or even babble. Birth was uneventful and there is no seizure or any mental retardation in the family. On examination, he was fair with light hair (Both parents are dark. However maternal aunt is fair), had microcephaly, microphthalmia, hypotonia with brisk reflexes. Pupils were normal. There was no red reflex. There was no organomegaly. Child was investigated and MRI brain, serum ammonia, blood gases, blood sugar and eye evaluation were normal. Chest X-Ray showed right lower zone pneumonia.
What is the cause of delayed milestones?
Expert Opinion :
This child has delayed development with microcephaly. He does not have any dysmorphic features ruling out a chromosomal abnormality. Also MRI brain is normal, this child does not have any organomegaly or chorioretinitis, thus congenital infection also seems unlikely. There is no adverse perinatal insult hence birth asphyxia also seems unlikely. An inborn error of metabolism is a possibility. However, baseline tests such as ammonia, blood sugar, blood gases and even MRI brain is normal. However, this child is fair with light hair which may suggest albinism. However pupils have no red reflex, thus oculocutaneous albinism seems unlikely. A metabolic disorder that causes fair skin, microcephaly and delayed development is phenylketonuria. This child was tested for same and Guthrie’s test was positive. Thus, always suspect phenylketonuria in a child with delayed development and abnormal features such as fair skin, microcephaly.