This little boy, Chen, was in good health when he was born. His newborn screen test result was normal.
His mother noticed his skin was turning yellow when he was one and a half months old. Initially, Chen was taken to other hospital for evaluation. The preliminary laboratory test showed abnormal liver function and direct type hyperbilirubinemia. Chen undergone a number of tests subsequently, including tests for infection, Wilson's disease, and autoimmune disease, but the results revealed no significant finding. Over the next three to four months, his liver enzyme and jaundice levels remained so high that the doctor suggested evaluation for liver transplantation would be the next step. Chen’s mother was shocked and unable to accept his son's need for a liver transplant, so she took him to our genetic counseling outpatient clinic for a second opinion.
Chen was about five months old when he came to our clinic. For infants with abnormal liver function and direct type hyperbilirubinemia, late-onset congenital metabolic diseases must be included in the differential diagnosis. Therefore, Chen received a repeated tandem mass spectrometry examination (the metabolic profile of newborn screening is measured by a tandem mass spectrometry), and result showed high levels of Citrulline in his blood. The further genetic test confirmed the diagnosis of Citrullinemia type II, which is a congenital disorder of deficiency of mitochondrial citrin protein to affect urea cycle metabolism that occurs from birth to adulthood. In infancy, the patient usually manifests with abnormal liver function and direct type hyperbilirubinemia. Our case, Chen, is a relative atypical case. The disease is included in neonatal screening, but cannot be detected during the neonatal period because of the potential for delayed onset.
After being diagnosed with Type II citrullinemia, Chen began to use special formula and nutritional adjustments. During follow-up, the liver function and hyperbilirubinemia gradually improved.
Chen is three years old at present, and his growth and intellectual development are normal. He is still regularly followed up in our clinic. Currently, he does not use special formula, but he still controls the disease according to the nutritional advice.
This case reminds us that when a patient presents with a suspected congenital metabolic disorder, even if the neonatal screening results was normal, we still need to put inborn errors of metabolism disorders into consideration, because some diseases may have delayed onset. Therefore, repeated tandem mass spectrometry always be a choice for those patients suspected to have congenital metabolic disorders.
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Genetic Counseling Center of Kaohsiung Veterans General Hospital
Hsiu-Jung Lee ／ Wan-Long Tsai ／ Pao-Chin Chou