Nov 13, 2023

The participant was born full-term after a normal pregnancy. She passed her newborn screening. She was healthy and developmentally on track until 2 months old. She began having generalized tonic-clonic seizures that were treated with levetiracetam. At this time, neurologic exams showed signs of rapid tongue movements (tongue fasciculations), increased muscle tone in the arms and legs (peripheral hypertonia), and low muscle tone throughout the rest of the body (hypotonia). She had a skin tag (preauricular tag) near her left ear and a bulge noted around her belly button (umbilical hernia).

Neurologic exams at 3 months showed a rapid in her ability to track objects with her eyes. Her seizures increased in frequency and required increased medications. She developed dry, scaley skin on her arms and legs. Further neurologic exams at 4 months showed significant developmental regression. She lost the ability to eat and had an NG tube placed. Her seizures continued to worsen. Her EEG tests were abnormal. Her brain MRI and CT were normal. She entered hospice care at 4 months and passed away at 5months.

This participant’s older brother passed away at 7 months and had similar symptoms. His newborn screening detected a partial biotinidase deficiency and he began 5mg biotin supplements shortly after birth. He had severe vomiting and wheezing (stridor) at 2 weeks. He was diagnosed with laryngomalacia (a softening of the tissue around the throat that causes wheezing). He started having seizures at 2 months that were uncontrollable by medication (intractable seizures). He began declining developmentally and had similar changes in muscle tone as his sister (hypotonia, peripheral hypertonia). He showed signs of hair loss and skin sloughing around his ears. Ultrasounds of his heart and kidneys were normal. MRI of his brain showed increased space for cereobrospinal fluid ,and his EEG testing was abnormal.

Both siblings:

• Failure to thrive
• Seizures (bilateral tonic-clonic seizures, abnormal EEGs)
• Muscle stiffness (spasticity)
• Increased muscle tone in limbs (limb hypertonia)
• Reduced deep tendon reflexes
• Developmental delay and regression

Sister Only:

• Crossed eyes (strabismus)
• Rapid tongue movement (Tongue fasciculations)
• Left ear tag (Preauricular skin tag)
• Hip dysplasia
• Umbilical hernia
• Skin discoloration (irregular hyperpigmentation)

Brother Only:

• Softening of tissue in the throat (Laryngomalacia)
• High pitched cry
• Partial Biotinidase deficiency
• Methylmalonic aciduria
• Skin detachment at neck
• Gastroesophageal reflux (GERD)

Sister:

• Clonazepam
• levetiracetam
• Lancosamide
• NG tube

Brother:

• Keppra
• Phenobarbital
• Trileptal