Familial posterior column ataxia (Biemond's) with scoliosis

Mutations in FLVCR1 cause posterior column ataxia and retinitis pigmentosa

The study of inherited retinal diseases has advanced our knowledge of the cellular and molecular mechanisms involved in sensory neural signaling. Dysfunction of two specific sensory modalities, vision and proprioception, characterizes the phenotype of the rare, autosomal-recessive disorder posterior column ataxia and retinitis pigmentosa (PCARP). Using targeted DNA capture and high-throughput sequencing, we analyzed the entire 4.2 Mb candidate sequence on chromosome 1q32 to find the gene mutated in PCARP in a single family. Employing comprehensive bioinformatic analysis and filtering, we identified a single-nucleotide coding variant in the feline leukemia virus subgroup C cellular receptor 1 (FLVCR1), a gene encoding a heme-transporter protein. Sanger sequencing confirmed the FLVCR1 mutation in this family and identified different homozygous missense mutations located within the protein's transmembrane channel segment in two other unrelated families with PCARP. To determine whether the selective pathologic features of PCARP correlated with FLVCR1 expression, we examined wild-type mouse Flvcr1 mRNA levels in the posterior column of the spinal cord and the retina via quantitative real-time reverse-transcriptase PCR. The Flvcr1 mRNA levels were most abundant in the retina, followed by the posterior column of the spinal cord and other brain regions. These results suggest that aberrant FLVCR1 causes a selective degeneration of a subpopulation of neurons in the retina and the posterior columns of the spinal cord via dysregulation of heme or iron homeostasis. This finding broadens the molecular basis of sensory neural signaling to include common mechanisms that involve proprioception and vision.

Isolated degeneration of the posterior column as a distinct entity--a clinical and electrophysiologic follow-up study

OBJECTIVE

The aim of the study was to better describe the long term clinical course and electrophysiologic and radiologic findings in isolated degeneration of the posterior column.

METHODS

Four patients with the presenting symptoms of a progressive tabetic ataxia were followed up clinically and electrophysiologically over up to 15 years between 1997 and 2008. They received standardized neurological examinations, electrophysiologic testing with SEP, MEP, NCV, EMG, autonomic testing and cardiac evaluation, head and spine MRI, laboratory evaluation including CSF analysis.

RESULTS

Progressive gait ataxia due to pallhypasthesia and loss of position sense with areflexia remained the only symptoms. Pes cavus deformity was a notable clinical feature in all cases. There was no involvement of other systems and all patients remained fully ambulatory. There was no cardiac involvement. Electrophysiology was characterized by absent cortical tibial SEP with normal lumbar complexes and normal nerve conduction studies and transcortical magnetic stimulation as well as sympathetic skin response. MRI of the cord was normal. Laboratory analysis and CSF were unrevealing.

CONCLUSION

Isolated degeneration of the posterior column is a rare condition with a clinically benign course without progression involving other systems and characteristic electrophysiologic findings (isolated loss of cortical tibial-SEP with normal lumbar leads). Pes cavus deformity seems to be an unusual but typical clinical feature. The etiology is most likely a sporadic degenerative disease of the cord.

Posterior column ataxia and retinitis pigmentosa: a distinct clinical and genetic disorder

Autosomal recessive posterior column ataxia and retinitis pigmentosa (PCARP) is a movement disorder that was genetically mapped to a disease locus (AXPC1) on chromosome 1q32-q31 in an inbred population of Dutch-German ancestry in the continental United States. We performed genetic linkage analysis and haplotype reconstruction on a different family from Spain with an identical phenotype to determine if the neurologic signs of an early-onset ataxia, retinitis pigmentosa, and a sensory neuropathy also mapped to the AXPC1 locus. The disease phenotype was linked in the candidate interval with a maximum lod score of 3.56 at a recombination fraction of 0.0 for locus D1S414. Haplotypes were discordant and suggested that the disease mutation arose independently from at least two populations. These results refine the classification of early-onset ataxia, abrogate a founder effect for this recessive disorder, and provide evidence that PCARP is a distinct, homogeneous, clinical, and genetic disorder.

Friedreich's ataxia presenting with pure sensory ataxia: a long-term follow-up study of two patients

We describe two patients with Friedreich's ataxia whose presenting symptomatology was for years progressive tabetic ataxia. Based upon the initial clinical, electrophysiological and nerve biopsy data, a diagnosis of idiopathic sensory neuropathy was established. Subsequent examination of the kin showed that three sisters of case 1 had Friedreich's ataxia. Upon serial clinical and electrocardiographic study, both patients eventually developed a florid Friedreich's ataxia, including cardiomyopathy. Our findings indicate that at onset Friedreich's ataxia may be indistinguishable from sensory neuropathy and also that serial examination and investigation of kinship are essential steps for accurate diagnosis.

A case of Charcot-Marie-Tooth disease mimicking Friedreich's ataxia: is there any association between friedreich's ataxia and Charcot-Marie-Tooth disease?

The authors report a case of Charcot-Marie-Tooth disease that mimicked Friedreich's ataxia and featured impaired tendon reflexes in the limbs, incoordination mimicking cerebellar disease in the extremities, extensor plantar responses on both sides, bilateral foot deformity, imparied position sense in the toes, absent vibratory sense in the distal parts of the legs and minimal distal weakness with wasting. Motor conduction velocity in the upper limbs was substantially reduced. Other cases similar in nature reported in the literature resemble spino-cerebellar degeneration in general, and Friedreich's ataxia, in particular. It is emphasized that the natural history, EMG, motor conduction velocity studies and examination of other affected members of the family permit the correct diagnosis to be made in such cases. It is also emphasized that patients similar to the one reported here may also resemble, and should be differentiated from, cases of familial dorsal column ataxia (Biemond type). Stress is put upon the fact that when Charcot-Marie-Tooth disease mimicks spino-cerebellar degeneration, substantial slowing of motor conduction in the upper limbs is generally sufficient to establish the diagnosis. The relation between Friedreich's ataxia an Charcot-Marie-Tooth disease is reviewed and it is concluded that these two disorders are distinct clinical and pathological entities.