Hypophosphatemic rickets: presenting features of fanconi-bickel syndrome

Endocrine involvement in hepatic glycogen storage diseases: pathophysiology and implications for care

Hepatic glycogen storage diseases constitute a group of disorders due to defects in the enzymes and transporters involved in glycogen breakdown and synthesis in the liver. Although hypoglycemia and hepatomegaly are the primary manifestations of (most of) hepatic GSDs, involvement of the endocrine system has been reported at multiple levels in individuals with hepatic GSDs. While some endocrine abnormalities (e.g., hypothalamic‑pituitary axis dysfunction in GSD I) can be direct consequence of the genetic defect itself, others (e.g., osteopenia in GSD Ib, insulin-resistance in GSD I and GSD III) may be triggered by the (dietary/medical) treatment. Being aware of the endocrine abnormalities occurring in hepatic GSDs is essential (1) to provide optimized medical care to this group of individuals and (2) to drive research aiming at understanding the disease pathophysiology. In this review, a thorough description of the endocrine manifestations in individuals with hepatic GSDs is presented, including pathophysiological and clinical implications.

Fanconi–Bickel syndrome in a Ugandan child – diagnostic challenges in resource-limited settings: a case report

Background

Fanconi–Bickel syndrome is an autosomal recessive disorder of glucose metabolism. It is an extremely rare disorder. Most cases have been reported in consanguineous communities. None of the cases have been reported in Black Africans in sub-Saharan Africa. This case was diagnosed 3 years after initial presentation due to diagnostic challenges and limited awareness of similar metabolic syndromes in our setting.

Case presentation

We report the case of a 4-year-old boy, born to non-consanguineous Black African parents, who presented with failure to thrive and rachitic features in infancy. Clinical, laboratory, and radiological features were indicative of Fanconi–Bickel syndrome. No genetic testing was done. The diagnosis was made 3 years after the initial presentation due to diagnostic challenges. He showed clinical improvement with the institution of a galactose-free diet.

Conclusion

Fanconi–Bickel syndrome occurs even in non-consanguineous Black African populations. Therefore, clinicians in resource-poor settings should raise their index of suspicion for such metabolic disorders in settings with a high prevalence of failure to thrive among children.

Fanconi-Bickel Syndrome: A Review of the Mechanisms That Lead to Dysglycaemia

Accumulation of glycogen in the kidney and liver is the main feature of Fanconi-Bickel Syndrome (FBS), a rare disorder of carbohydrate metabolism inherited in an autosomal recessive manner due to SLC2A2 gene mutations. Missense, nonsense, frame-shift (fs), in-frame indels, splice site, and compound heterozygous variants have all been identified in SLC2A2 gene of FBS cases. Approximately 144 FBS cases with 70 different SLC2A2 gene variants have been reported so far. SLC2A2 encodes for glucose transporter 2 (GLUT2) a low affinity facilitative transporter of glucose mainly expressed in tissues playing important roles in glucose homeostasis, such as renal tubular cells, enterocytes, pancreatic β-cells, hepatocytes and discrete regions of the brain. Dysfunctional mutations and decreased GLUT2 expression leads to dysglycaemia (fasting hypoglycemia, postprandial hyperglycemia, glucose intolerance, and rarely diabetes mellitus), hepatomegaly, galactose intolerance, rickets, and poor growth. The molecular mechanisms of dysglycaemia in FBS are still not clearly understood. In this review, we discuss the physiological roles of GLUT2 and the pathophysiology of mutants, highlight all of the previously reported SLC2A2 mutations associated with dysglycaemia, and review the potential molecular mechanisms leading to dysglycaemia and diabetes mellitus in FBS patients.