Novel mutations in Indian patients with autosomal recessive infantile malignant osteopetrosis

Department of Medical Genetics, Sanjay Gandhi Postgraduate Institute of Medical Sciences, Lucknow, India.
The Indian Journal of Medical Research (Impact Factor: 1.4). 04/2010; 131(4):508-14.
Source: PubMed


Although clinical reports have described infantile malignant autosomal recessive osteopetrosis (ARO) in Indian patients, no published data are available about the genetic causes of ARO in this population. We investigated the main genetic causes of ARO in eight Indian patients with early postnatal onset and the typical severe clinical course including visual impairment and anaemia.
Mutation screening in the genes CLCN7 and TCIRG1 was done on genomic DNA from 8 affected individuals (diagnosed on the basis of clinical and haematological parameters and characteristic radiological changes of increased bone density) and their parents. In one family, after detection of both mutations in the proband, targeted mutation analysis was also done in chorionic villus samples for prenatal diagnosis.
Six patients had mutations in TCIRG1 and two patients harboured mutations in CLCN7 gene. Three of the five different TCIRG1 mutations identified and both CLCN7 mutations were novel mutations. Except for the already known mutation p.Ile720del, all TCIRG1 mutations disrupt conserved splice consensus sequences or lead to premature stop codons. In contrast, both CLCN7 mutations only lead to missense changes of conserved amino acids. In a foetus harbouring TCIRG1 mutations osteopetrosis was visible radiologically at 23 wk of gestation.
That the CLCN7 mutations provoke a phenotype as severe as the one caused by TCIRG1 loss of function suggests the affected residues to be crucial for the function of the ClC-7 chloride channel or chloride/proton-exchanger. Our data also show that ARO can manifest as early as in the second trimester of pregnancy.

    • "MIOP is a fatal disorder with an incidence of 1:200,000-1:300,000.[1] In most of the patients, the recessive form occurs due to mutations in the gene encoding an osteoclastic specific subunit of the vacuolar proton pump, thereby causing disturbances in acidification needed for normal osteoclast function.[3] Most patients present with symptoms within the first year of life. "
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    ABSTRACT: Osteopetrosis is a rare congenital disorder of bone resorption, caused by failure of osteoclasts to reabsorb immature bone. Malignant infantile osteopetrosis presents in early life with generalized osteosclerosis and decreased bone marrow spaces, resulting in anemia, splenohepatomegaly due to extramedullary hematopoiesis, cranial nerve compression, and growth failure. It is a fatal condition with death occurring within the first year of life. Bone marrow transplant remains the only curative treatment. We present a report of an infant with splenohepatomegaly, who was diagnosed with malignant infantile osteopetrosis.
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    Preview · Article · Apr 2010 · The Indian Journal of Medical Research
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    ABSTRACT: Osteopetrosis is a heterogenous group of disorders characterised by a failure of normal bone maturation and abnormal bone sclerosis secondary to the failure of osteoclasts to resorb bone. The most serious consequences of this disorder affect the nervous system. Patients with infantile osteopetrosis (also called malignant osteopetrosis) can develop a gradual occlusion of, or narrowing of the skull foramina at the skull base, resulting in the compression of vital nerves and vessels. Hydrocephalus has been identified in these patients, particularly those with the autosomal recessive variety of osteopetrosis. Although the exact aetiology is uncertain, it is possible that venous outflow obstruction at the cranial foramina along with a reduced intracranial space for cerebrospinal fluid (CSF) to flow around the hemispheres could be contributing factors. There are few reports in the literature on the management of this unusual association, hydrocephalus secondary to osteopetrosis. The authors report one such case where this association has been successfully surgically treated with endoscopic third ventriculostomy as a form of CSF diversion. We successfully treated a 9-month-old girl with osteopetrosis and symptomatic hydrocephalus with an endoscopic third ventriculostomy (ETV). She later went on to have stem cell transplantation to treat the osteopetrosis. Most reports in the literature have identified ventriculoperitoneal (or other distal site) shunting as the treatment of choice for hydrocephalus in this setting. We would like to highlight that ETV is another effective and often very suitable method of CSF diversion in these patients.
    No preview · Article · May 2011 · Child s Nervous System
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