Patients with spinal muscular atrophy (SMA) type 2 have a high risk of hypoglycemia, hyperketosis, and metabolic acidosis during prolonged fasting. They also have disturbed fat and glucose metabolism. These are the results of a study by researchers in Denmark that appeared in Acta Paediatrica.

According to Mette C Ørngreen and the co-authors of the study, low skeletal muscle mass is the best explanation for why this happens.

These findings are important because they have implications for children facing surgery and those with severe illness. “Medical staff must be aware of the increased risk of metabolic crisis during prolonged fasting before surgery and when combined with a severe illness and low energy intake in patients with SMA [type 2],” the researchers wrote.

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In order to explore the metabolic mechanisms behind reported episodes of metabolic crisis in patients with SMA type 2, the team of researchers used a technique called stable isotope as well as indirect calorimetry to assess fat and glucose metabolism over a 24-hour fast or until hypoglycemia occurred in 4 adolescents, aged 15 to 17 years, and 6 adults, aged 19 to 37 years, with SMA type 2. They compared these to fat and glucose metabolism in 8 adults without the disease, aged 21 to 41 years.

The results showed that the patients with SMA type 2 developed moderate to severe hyperketosis while none of the healthy controls did. More than half of the SMA patients (60%) also had symptoms of hypoglycemia, which again did not occur in any of the healthy controls. 

In patients with SMA type 2, plasma bicarbonate levels decreased in line with increased ketone bodies, indicating the start of metabolic acidosis.

During the fasting period, healthy controls increased their fat production and utilization. This did not occur in patients with SMA type 2, which indicated blunted fat oxidation, according to the authors.

“Our study indicated that patients with SMA [type 2] struggled with a major energy crisis during fasting,” the authors concluded.


Ørngreen MC, Andersen AG, Eisum AS, et al. Prolonged fasting-induced hyperketosis, hypoglycaemia and impaired fat oxidation in child and adult patients with spinal muscular atrophy type II. Acta Paediatr. Published online August 18, 2021. doi:10.1111/apa.16074