Maple syrup urine disease in a neonate: a case report and literature review

Abstract

Objective To study the clinical characteristics of neonatal maple syrup urine disease (MSUD), and to improve the clinical recognition of the disorder. Methods Clinical and laboratory data of a case of a newborn MSUD admitted to the Hospital was retrospectively studied, literature and articles on MSUD in the local medical journals from January 1988 till October 2015 in China were reviewed. Clinical characteristics, diagnosis, treatment and prognosis of neonatal MSUD were summarized. Results From our literature search, we found 33 reported articles with a total of 39 cases of MSUD. Together with our case report, we have a total of 40 cases reports so far. There were 28 males and 12 females. The diagnosis was confirmed from 1 to 15 d after birth, an average of 5.6 d. Similar symptoms family history was seen in 11 cases (27.5%). All the 40 cases had the symptom of poor feeding (100%). 31 cases showed poor responses to stimulation (77.5%), 21 cases had odor of maple syrup (52.5%), and 35 cases had dysmyotonia (87.5%). 19 cases were misdiagnosed (47.5%). Laboratory findings showed acidosis occurred in 23 cases (57.5%), hyperammonemia in 15 cases (37.5%), and hypoglycaemia in 9 cases (22.5%), respectively. Blood or urine branched-chain amino acid levels were screened in 40 cases (100%), blood or urine branched-chain amino acid increased in all cases. Signal abnormality on brain MRI was detected in 17 cases (42.5%). BCKDHA gene mutations in different level were detected in 7 cases (17.5%). Mechanical ventilation was required in 18 cases (45.0%), hemodialysis treatment in 1 case (2.5%), Vitamin B1 treatment in 21 cases, and branched-chain amino acids free formula milk and L-carnitine treatment in 14 cases (35.0%). 18 cases had withdrawal treatment (45.0%). 33 cases were followed up (82.5%), 22 cases died (66.7%), 11 cases improved (33.3%) including mental retardation in 6 cases, infantile spasms in 1 case, and healthy in 4 cases. Conclusion The clinical phenotype of neonatal MSUD in China belongs to the classical type currently. It occurs with non-specific symptoms such as anorexia, milk refusal, poor responses and lethargy. The disorder can be misdiagnosed. Some cases have a similar family history. With the progression of the disease and without appropriate therapy, most of them had abnormal muscle tone, odor of maple syrup, and frequent convulsions. This disease has a high mortality and disability rate. Suspected patients should have blood or urine branched-chain amino acid levels tested and brain MRI as early as possible to enable early diagnosis, thus improvement in prognosis. Key words: Maple syrup urine disease; Inborn error of metabolism; Infant, newborn