Mutation in the novel nuclear-encoded mitochondrial protein CHCHD10 in a family with autosomal dominant mitochondrial myopathy.

Mitochondrial myopathies belong to a larger group of systemic diseases caused by morphological or biochemical abnormalities of mitochondria. Mitochondrial disorders can be caused by mutations in either the mitochondrial or nuclear genome. Only 5% of all mitochondrial disorders are autosomal dominant. We analyzed DNA from members of the previously reported Puerto Rican kindred with an autosomal dominant mitochondrial myopathy (Heimann-Patterson et al. 1997). Linkage analysis suggested a putative locus on the pericentric region of the long arm of chromosome 22 (22q11). Using the tools of integrative genomics, we established chromosome 22 open reading frame 16 (C22orf16) (later designated as CHCHD10) as the only high-scoring mitochondrial candidate gene in our minimal candidate region. Sequence analysis revealed a double-missense mutation (R15S and G58R) in cis in CHCHD10 which encodes a coiled coil-helix-coiled coil-helix protein of unknown function. These two mutations completely co-segregated with the disease phenotype and were absent in 1,481 Caucasian and 80 Hispanic (including 32 Puerto Rican) controls. Expression profiling showed that CHCHD10 is enriched in skeletal muscle. Mitochondrial localization of the CHCHD10 protein was confirmed using immunofluorescence in cells expressing either wild-type or mutant CHCHD10. We found that the expression of the G58R, but not the R15S, mutation induced mitochondrial fragmentation. Our findings identify a novel gene causing mitochondrial myopathy, thereby expanding the spectrum of mitochondrial myopathies caused by nuclear genes. Our findings also suggest a role for CHCHD10 in the morphologic remodeling of the mitochondria.

Cranial nerve palsies in renal osteodystrophy.

There is a wide differential diagnosis for patients presenting with multiple cranial nerve palsies, including infectious, inflammatory, malignant, genetic, toxic, and metabolic conditions. This report describes the clinical features, neuroimaging findings, and response to surgical treatment in a patient with bilateral deafness and recurrent episodes of bilateral facial nerve palsy that were caused by renal osteodystrophy. It is suggested that renal osteodystrophy be considered in the differential diagnosis of multiple cranial nerve palsies in the appropriate clinical setting.

Ischemic stroke in the setting of tuberculous meningitis.

The clinical syndrome of tuberculous (TB) meningitis leading to ischemic strokes is rarely seen today in immunocompetent adults native to North America. This entity is also notoriously difficult to diagnose because the presenting symptoms are often nonspecific. The authors describe a case of a man with TB meningitis which progressed to recurrent ischemic cerebral infarcts.

Focal occipital seizures with cerebral polyopia.

Polyopia is the visual perception of multiple images of a single visual stimulus. Cerebral polyopia has previously been described as an ictal phenomenon associated with temporal lobe seizures. We report the case of a man with multiple cavernous angiomas and occipital lobe seizures manifesting as cerebral polyopia.

Phenotypic features and genetic findings in sacsin-related autosomal recessive ataxia in Tunisia.

BACKGROUND: Autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS) is a clinically homogenous disorder reported in Quebec caused by mutations in the SACS gene (chromosome 13q12). Recently, we identified a Tunisian kindred demonstrating linkage to the ARSACS locus. OBJECTIVE: To report clinical, neurophysiological, and nerve biopsy findings in patients with autosomal recessive cerebellar ataxia related to the SACS gene in Tunisia. PATIENTS AND METHODS: Genetic linkage analysis of patients with early-onset autosomal recessive cerebellar ataxia allowed the identification of 4 families from which 18 patients demonstrated linkage to the ARSACS locus. The patients were evaluated according to the International Cooperative Ataxia Rating Scale. Peripheral nerve conduction, sensory evoked potentials, and nerve biopsy were performed in most patients. RESULTS: The mean age at onset was 4.5 years. The clinical phenotype was stereotyped and associated with a progressive cerebellar syndrome, a pyramidal syndrome with brisk knee reflexes, and Babinski sign and absent ankle reflexes. The course of the disease varied among patients. Sensory evoked potentials showed severe posterior column involvement. Peripheral nerve investigations demonstrated axonal and demyelinating neuropathy. Four mutations, 2 missense and 2 nonsense, were found. CONCLUSION: In Tunisia, autosomal recessive cerebellar ataxia related to the SACS gene demonstrated a homogenous phenotype and heterogeneous allelic mutations.