Identification of new mutations in TCIRG1 as a cause of infantile malignant osteopetrosis in two Mexican patients

Abstract

Background: Osteopetrosis is a heterogeneous group of diseases that are characterized by increased bone density due to abnormalities in osteoclast differentiation or function, which result in a lack of bone resorption. Case reports: Two patients with osteopetrosis onset since the first months of life, with facial dysmorphia, blindness, deafness, hepatosplenomegaly, hypotonia, neurodevelopmental retardation and bicytopenia. Bone radiographs showed osteosclerosis. They were assessed by different specialists prior to definitive diagnosis. Genetic analysis determined mutations in the TCIRG1 gene. Patient 1 had a homozygous mutation for p.Ile720Alafs*14 identified, which hasn't been previously reported. Patient 2 had a compound heterozygous mutation: the first one, p.Phe459Leufs*79, and the second one, p.Gly159Argfs*68, none of which has been previously reported as far as we know. Conclusion: The only therapeutic option for patients with osteopetrosis is hematopoietic stem cell transplantation (HSCT), which should be carried out in the course of the first 3 months of life, before neurological damage occurs. Although osteopetrosis diagnosis is relatively simple, it is delayed owing to the lack of clinical suspicion.