# Clinical Outcomes and Management in Late Diagnosed Siblings Affected With Attenuated GSD Ib

## TL;DR

Two siblings with GSD1b were diagnosed in adulthood due to atypical symptoms, showing how the disease can present differently and later than usual.

## Contribution

First reported cases of GSD1b diagnosed in adulthood without typical early symptoms like hypoglycaemia or neutropenia.

## Key findings

- Siblings with GSD1b were diagnosed in adulthood after showing non-hypoglycaemic complications.
- One sibling developed cirrhosis during adolescence while the other had gout and nephrolithiasis.
- Empagliflozin treatment corrected mild neutropenia in one patient.

## Abstract

Glycogen storage disease 1b (GSD1b) typically presents in early infancy with poor fasting tolerance, hepatomegaly, and neutropenia. We report two siblings who were diagnosed with GSD1b in adulthood. Both had a normal fasting tolerance throughout childhood and, as adults, were able to fast for at least 16 h without developing hypoglycaemia. The older sibling developed nodular cirrhosis during adolescence. The younger sibling exhibited a more pronounced metabolic phenotype, including hyperuricaemia leading to recurrent gout and nephrolithiasis. He experienced occasional episodes of mild neutropenia that were corrected with empagliflozin treatment. To our knowledge, these represent the first reported patients with GSD1b presenting in adulthood with non‐hypoglycaemic complications of the disease and without overt neutropenia or neutrophil dysfunction.

GSD1b usually presents in early childhood with hypoglycaemia, lactic acidosis, hepatomegaly and neutropenia.GSD1b patients can rarely withstand prolonged fasting periods without hypoglycaemic symptoms. The absence of these symptoms contributed to the late diagnosis in these two patients.Differing phenotypes and severity can be present even in the same underlying GSD1b genotype.

GSD1b usually presents in early childhood with hypoglycaemia, lactic acidosis, hepatomegaly and neutropenia.

GSD1b patients can rarely withstand prolonged fasting periods without hypoglycaemic symptoms. The absence of these symptoms contributed to the late diagnosis in these two patients.

Differing phenotypes and severity can be present even in the same underlying GSD1b genotype.