Neuromyelitis optica (Devic's syndrome): no association with the primary mitochondrial DNA mutations found in Leber hereditary optic neuropathy

Familial neuromyelitis optica

BACKGROUND

Detection of aquaporin-4-specific immunoglobulin G (IgG) has expanded the spectrum of neuromyelitis optica (NMO). Rare reports of familial aggregation have suggested a component of genetic susceptibility but these reports mostly antedated the discovery of the NMO-IgG biomarker and recently updated diagnostic criteria.

METHODS

We report a case series describing the demographic, clinical, neuroimaging, and NMO-IgG serologic status of 12 multiplex NMO pedigrees with a total of 25 affected individuals.

RESULTS

Twenty-one patients (84%) were women. Families were Asian (n = 5), Latino (n = 4), white (n = 1), or African (n = 2). Apparent transmission was either maternal (n = 5) or paternal (n = 2). In 1 family, 3 individuals had NMO; in the others, 2 individuals were affected. Sibling pairs (n = 6), parent-child (n = 4), and aunt-niece (n = 3) pairs were observed. Nineteen patients (76%) were NMO-IgG positive. Twelve (48%) had clinical or serologic evidence of another autoimmune disease. Familial occurrence of NMO occurs in approximately 3% of patients with well-established diagnosis of NMO.

CONCLUSIONS

A small proportion of patients with NMO have relatives with this condition, but familial occurrence is more common than would be expected from its frequency in the general population. Familial NMO is indistinguishable from sporadic NMO based on clinical symptoms, age at onset, sex distribution, and frequency of NMO-IgG detection. One or 2 generations were affected and affected individuals represented a small fraction of family members. Taken together, these data suggest complex genetic susceptibility in NMO.

Review: Mitochondria and disease progression in multiple sclerosis

Multiple sclerosis (MS) is an inflammatory demyelinating disease of the central nervous system. Recent evidence suggests that dysfunction of surviving demyelinated axons and axonal degeneration contribute to the progression of MS. We review the evidence for and potential mechanisms of degeneration as well as dysfunction of chronically demyelinated axons in MS with particular reference to mitochondria, the main source of adenosine-5'-triphosphate in axons. Besides adenosine-5'-triphosphate production, mitochondria play an important role in calcium handling and produce reactive oxygen species. The mitochondrial changes in axons lacking healthy myelin sheaths as well as redistribution of sodium channels suggest that demyelinated axons would be more vulnerable to energy deficit than myelinated axons. A dysfunction of mitochondria in lesions as well as in the normal-appearing white and grey matter is increasingly recognized in MS and could be an important determinant of axonal dysfunction and degeneration. Mitochondria are a potential therapeutic target in MS.

Neuromyelitis optica — Devic's syndrome, update

Neuromyelitis optica of Devic (NMO) is a syndrome which combines transverse myelitis and optic neuritis. For many years it was assumed that transverse myelitis and optic neuritis should be simultaneous, that optic neuritis should be bilateral, and that transverse myelitis must be complete. NMO was considered to be very rare. Through the 20th century there was a debate on whether NMO is a distinct nosologic entity or a form of MS. In 2005 it is now possible to distinguish NMO from MS on the basis of the clinical, imaging, serology and immunopathology profile. This distinction is necessary for the implementation of adequate treatments, as the relapsing form of the illness carries significant morbidity and mortality.

Visual recovery in a man with the rare combination of mtDNA 11778 LHON mutation and a MS-like disease after mitoxantrone therapy

We describe a young man with prognostic unfavourable homoplasmatic mitochondrial DNA(mt DNA) 11778 Leber's hereditary optic neuropathy (LHON) point mutation and confirmed multiple sclerosis (MS). This combination of LHON and MS-like disease is rare in both sexes, and in men has been described in only a few case reports. In a 4-year follow-up during immunosuppressive therapy with mitoxantrone, we found a remarkable time delayed visual recovery 12 months after acute onset of rapid sequential bilateral subtotal visual loss followed by episodes of isolated acute demyelinative optic neuropathy. Visual recovery to such extent after this latency is uncommon in both mtDNA 11778 LHON mutation and optic neuritis (ON) in MS. Relapses in visual deterioration must be considered as extremely rare in LHON. This case might support the hypothesis of an immunological pathogenetic factor in combined LHON and MS, and possibly in LHON alone. We suggest a search for the LHON mutation in MS patients with predominant visual impairment, independent of patients' gender.

Inheritance of susceptibility to multiple sclerosis

In recent years, epidemiological evidence supporting the genetic basis of multiple sclerosis has been extended and whole-genome linkage screening has advanced the mapping of the involved genes. Understanding of the known HLA associations has also improved and many candidate genes have been studied.