[Analysis of clinical features of 6 patients with infantile type glycogen storage disease type II]

To summarize clinical features and diagnosis of Chinese infantile patients with glycogen storage disease type II (GSD II).

Six infant patients with GSD II diagnosed from January 2012 to June 2014 in the Department of Pediatrics, Peking University First Hospital were enrolled into this study. Clinical information of the 6 patients, including clinical manifestation, blood biochemistry, chest X-ray, echocardiogram, electrocardiogram, acid alpha-glucosidase (GAA) activity and GAA gene mutation analysis by direct sequencing of polymerase chain reaction (PCR) product were reviewed.

Of the 6 patients, five were female and one was male, five of whom were classic infantile type while the other one was atypical. The age of onset ranged from birth to 3-month-old. All patients had varying degrees of generalized muscle weakness, hypotonia and development retardation or retrogression. Other common findings were feeding difficulties in two patients, tongue weakness in two patients, respiratory distress in four patients, macroglossia in one patient, and hepatomegaly in two patients. Left ventricular hypertrophy and cardiomegaly were obvious in all the six patients. All six patients were found to have a enlarged heart in physical examination, and three patients who underwent a chest X-ray examination had an enlarged heart shadow. Four patients who had an echocardiography were found to have myocardial hypertrophy. The electrocardiogram in three patients showed short PR intervals and high voltage. The creatine kinase (CK) levels were three to seven times elevated. The mildest elevated CK was 441 IU/L, and the highest CK level was 1 238 U/L. Assay of GAA enzyme activity in whole blood showed significantly reduced activity (1.3 nmol/ (spot·d) to 2 nmol/(spot·d)) in the patients tested. Gene sequencing in 4 patients showed 8 pathogenic mutations, including 6 missense mutations, one nonsense mutation and one frameshift mutation. The missense mutations were c.998C > A (p.Thr333Lys), c.1280T > C (p.Met427Thr), c.1760T > C (p.Leu587Pro), c.1924G > T (p.Val642Phe), c.2012T > A (p.Met671Lys) and c.2105G > A (p.Arg702His). The nonsense mutation was c2662G > T (p.Glu888X), and the frameshift mutation was c2812_2813delTG (p.Cys938fs). The 5 classic infantile patients died at the age of 7 to 22 months. The atypical infantile patient was 2 years and five months old according to our latest follow up.

Infantile GSD II had similar motor manifestations and cardiac involvements, blood biochemical test, imaging findings, enzyme assays, though there were slight differences. The probability of GSD II should be taken into consideration if an infant has both muscular disease and cardiac involvement.