FNIP1-associated syndrome

Any immunodeficiency in which the cause of the disease is a mutation in the FNIP1 gene, characterized by onset of recurrent viral and bacterial infections, particularly with encapsulated bacteria, and hypertrophic cardiomyopathy in the first months or years of life. Immunologic workup typically shows decreased circulating B cells and hypo- or agammaglobulinemia, sometimes with neutropenia or T-cell lymphocytosis, although laboratory findings may be variable among patients. Ig replacement therapy is beneficial. Cardiac involvement can also include atrial septal defect, valvular insufficiency, and pre-excitation syndrome. Rare myopathic or neurologic involvement has been reported, but these features are not consistently part of the disorder and may be related to other genetic defects. Disruption of Folliculin Interacting Protein 1 alters the essential metabolic regulators AMPK and mTOR, resulting in profound B-cell deficiency, hypertrophic cardiomyopathy, and pre-excitation syndrome.