background participants

Participant 121

On this page, you will find information about a UDN participant.

Sharing information on this website is not a requirement of UDN participation. Only descriptions about participants who give explicit consent will appear here. While these participant pages are helpful to understand our participants’ stories, they do not begin to describe their diagnostic odysseys. A special thank you goes out to our participants and their families for sharing their experiences.


Male, age 4 with global developmental delay, decreased muscle tone (hypotonia), delayed brain development (delayed myelination), visual impairment, and a large head size (macrocephaly)

Date of Report

Apr 08, 2019


The participant was born with an undescended testis (unilateral cryptorchidism) and scrotal webbing but was otherwise healthy. When he was 6 weeks old, his parents became concerned that he seemed less alert. An eye exam at this time showed that he had visual impairment. He was also noticed to have developmental delays and decreased muscle tone (hypotonia).

At 12 months old, the participant was hospitalized because he was having seizures. While in the hospital, he was found to have low sodium levels. A brain MRI performed at 18 months showed delayed brain development (myelination). The participant is now 4 ½ years old and can feed himself with a fork. He walks with assistance, but he has taken up to 100 independent steps, and he tires easily when walking. He is non-verbal but is learning to use assistive technologies to communicate.

The participant’s sister has some similar symptoms. It is currently unclear if they have the same condition or a different condition.

Symptoms / Signs
  • Global developmental delay
  • Expressive language delay
  • Decreased muscle tone (hypotonia, axial>appendicular)
  • Delayed brain development (delayed myelination)
  • Visual impairment (cerebral)
  • Large head size (macrocephaly)
  • Seizures with low sodium levels (hyponatremia)
  • Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
  • Broad forehead
  • Eye abnormalities (exotropia of left eye, small optic nerve cups, dissociated vertical deviation, bright blue irides, downslanting palpebral fissures)
  • Bumps on tongue (tongue nodules)
  • Facial muscle weakness (myopathic facies)
  • Inverted nipples
  • Genital abnormalities (unilateral cryptorchidism, scrotal webbing)
  • Swelling (edema) and redness (dependent rubor) of hands and feet
Current Treatments
Prior Treatments
  • Dilantin, Keppra – seizures
  • Urea –  SIADH
Considered treatments
Previously Considered Diagnoses
  • Chromosome disorder
  • Congenital disorder of glycosylation
  • Megalocornia (due to CHRDL1 variants – X-linked)
  • Metabolic disorder
  • Mitochondrial disorder
  • Tuberous sclerosis (due to TSC1 variant)
Other Photographs
Genetic Variants of Interest

If this participant sounds like you or someone you know, please contact us!


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