Infantile Fructose-1,6-Bisphosphatase Deficiency Masquerading as Mitochondriopathy

Fructose-1,6-bisphosphatase 1 (FBP1) deficiency is a rare autosomal recessive disorder of gluconeogenesis. Affected children present with severe hypoglycemia and lactic acidosis in infancy. We report a case of a female child, aged one year and six months, born out of a third-degree consanguineous marriage, who initially presented with sudden-onset vomiting episodes and failure to thrive. Despite a clinical suspicion of mitochondrial disorder, biochemical investigations revealed elevated levels of alanine, glycine, lactic acid, pyruvic acid, 3-hydroxy isovaleric acid, fumaric acid, and 4-hydroxy phenylacetic acid. Clinical exome sequencing confirmed homozygous inheritance of a mutated