Dataset Information

Cranial MR spectroscopy of tetrahydrobiopterin deficiency.

ABSTRACT:

Background and purpose

Severe and progressive neurologic disease remains a problem for patients with hyperphenylalaninemia due to a deficiency of tetrahydrobiopterin (BH4), even with early diagnosis and despite treatment with BH4 and neurotransmitter precursors. Few reports have included the associated imaging characteristics. Our purpose was to describe the imaging features of BH4-deficient patients identified by neonatal screening in a Taiwanese population and to correlate the imaging features with the treatment.

Methods

This study analyzed the cases of eight BH4-deficient patients who were examined by MR imaging and MR spectroscopy. Analysis of the findings was correlated with the clinical findings.

Results

One patient whose intelligence quotient score was lower than those of the other seven patients experienced seizures in conjunction with central white matter signal changes on MR images and a lactate peak on MR spectroscopy. Lactate peak was revealed in another patient who had marked elevations of N-acetylaspartate:creatine and N-acetylaspartate:choline ratios. Although most patients had a higher than average N-acetylaspartate:creatine or N-acetylaspartate:choline ratio, the patient who had decreases of both ratios possessed the highest intelligence quotient scores among the eight patients. In addition, the myoinositol:choline ratio correlated positively with the average BH4 dosage (P =.027, r = 0.027) and the choline:creatine ratio correlated negatively with the average 5-hydroxytryptophan dosage (P =.035, r = -0.742).

Conclusion

Compared with classical phenylketonuria, patients with BH4 deficiency have fewer white matter changes revealed by MR imaging but more changes revealed by MR spectroscopy. MR spectroscopy is a potential method with which to monitor the dosages of supplements used to treat this disorder. In addition, MR spectroscopy may be helpful in gaining understanding of the neurophysiological changes that occur in association with this disease.

SUBMITTER: Chien YH

PROVIDER: S-EPMC7976926 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundTetrahydrobiopterin (BH4) deficiency is a rare cause of hyperphenylalaninemia (HPA). The incidence of this condition varies based on region and ethnicity. In the early stages, patients typically do not exhibit any symptoms, and HPA is identified only through newborn screening for diseases. It is important to distinguish BH4 deficiency from phenylketonuria (PKU, MIM # 261600). Timely diagnosis and treatment of BH4 deficiency are crucial for the prognosis of patients.Case presentationWe present two rare cases of Chinese Tibetan children with BH4D, diagnosed through biochemical tests and genetic sequencing. Case 1 is a male infant, 2 months old, with a newborn screening (NBS) Phe level of 1212 μmol/L (reference range <120 μmol). The biopterin(B) level was 0.19 mmol/molCr (reference range: 0.42-1.92 mmol/molCr), with a B% of 5.67% (reference range: 19.8%-50.3%). Gene sequencing revealed a homozygous missense variant [NM_000317.3 (PTS): c.259C > T (p.Pro87Ser), rs104894276, ClinVar variation ID: 480]. The patient was treated with a Phe-reduced diet and oral sapropterin, madopar and is currently 3 years and 4 months old, showing mild global developmental delay. Case 2 is a 40-day-old female infant with a Phe level of 2442.11 μmol/L and dihydropteridine reductase (DHPR) activity of 0.84 nmol/(min. 5 mm disc) (reference range: 1.02-3.35 nmol/min.5 mm disc. Gene sequencing revealed a compound heterozygous genotype [NM_000320.3(QDPR): c.68G > A (p.Gly23Asp), rs104893863, ClinVar Variation ID: 490] and [NM_000320.3(QDPR) c.419C > A (p. Ala140Asp), ClinVar ID: 2444501]. The patient was treated with a Phe-reduced diet and oral madopar, 5-hydroxytryptophan. At the age of 1 year, she exhibited severe global developmental delay with seizures.ConclusionWe identified and treated two cases of BH4D in Tibetan populations in China, marking the first confirmed instances. Our report emphasizes the significance of conducting differential diagnosis tests for BH4D.