Safety and Efficacy of Metformin for Treatment of Cytopenia in Children and Adolescents With Fanconi Anemia

Inclusion Criteria: * Age: 5 to 18 years * Patients who are diagnosed with Fanconi anemia based on clinical features and confirmed by increased chromosomal breakage on diepoxybutane (DEB) stress testing. * Presence of cytopenia (at least one of the following: hemoglobin (Hb) \< 10 g/dL, platelet count \< 100 x 109/L, or an absolute neutrophil count (ANC) \< 1.0 x 109/L * Patients receiving other therapies e.g., androgens are eligible for enrollment after a one-month washout period before the start of metformin. Exclusion Criteria: * Patients who underwent bone marrow transplantation. * Patients with evidence of myelodysplasia, leukemia, or other concurrent malignancy. * Patients who have a history of allergic reactions to metformin or similar compounds. * Patients with a history of symptomatic hypoglycemia over the past year or hypoglycemia \< 50 mg/dL on screening and baseline laboratory assessments. * Patients with type 1 diabetes mellitus. * Patients with vitamin B12 deficiency. * Patients with Glucose-6-Phosphate Dehydrogenase deficiency. * Patients with abnormal Kidney function tests including serum creatinine, elevated liver function tests including live enzymes (ALT or AST \> 135 U/L, total bilirubin \> 1.5 x upper limit of normal for age, and/or patients with metabolic acidosis (bicarbonate \< 17 meq/L on venous blood gases).