Genetic Variants and Clinical Features of Patients With Glycogen Storage Disease Type Ib.

IMPORTANCE

Glycogen storage disease type Ib (GSDIb) is a rare metabolic disorder characterized by impaired glucose-6-phosphate transporter function with limited descriptions.

OBJECTIVE

To describe the genetic and clinical features of Chinese patients with GSDIb.

DESIGN, SETTING, AND

PARTICIPANTS

This retrospective cohort study retrieved the medical records of 113 Chinese patients with GSDIb treated at a single institution in Shanghai from November 1, 2000, to June 30, 2024.

MAIN OUTCOMES AND MEASURES: Biochemical parameters and clinical features (infections, inflammatory bowel disease [IBD], kidney and cardiovascular issues, growth and puberty) at baseline and the last follow-up, all-cause mortality, and mental and social development were assessed.

RESULTS

A total of 113 patients (96 children [85%]; 67 males [59%]) had GSDIb genetically diagnosed at a median age of 1.4 (range, 0.0-35.5) years. Thirty-eight novel SLC37A4 variants were identified. Hypoglycemia and metabolic derangements were the primary concerns in patients aged 2 years or younger (45%). Short stature (75%), infections (75%), and recurrent epistaxis (31%) became more prevalent in patients aged 2.1 to 5.0 years. The frequency of respiratory tract infection decreased after a median age of 7.0 (IQR, 3.5-10.5) years. Forty-four patients (46%) developed IBD at a median age of 6.0 (IQR, 3.0-12.0) years, 14% of whom developed IBD-associated arthritis at a median age of 10.5 (IQR, 5.8-19.6) years. The mean (SD) difference between the z scores of actual height and target height (Δ height z scores) at the final visit (-2.11 [1.76]) did not significantly increase even after uncooked cornstarch treatment. The mean (SD) Δ height z scores of the patients with IBD (-2.99 [1.70]) were significantly lower than those without IBD (mean [SD], -1.36 [1.44]) (P < .001). Ten patients (9%) died due to complications of GSDIb, including metabolic derangements, sepsis, and/or severe pneumonia (n = 8), IBD (n = 1), and pulmonary hypertension (n = 1).

CONCLUSIONS AND RELEVANCE: In this cohort study, the genetic and clinical spectra of GSDIb were broadened, suggesting associations between GSDIb and bowel, growth, and survival outcomes. To date, no previous study reported IBD-associated arthritis.