Cerebellar ataxia, myoclonus, cervical lipomas, and MERRF syndrome. Case report

Abnormalities of Skin and Cutaneous Appendages in Neuromuscular Disorders

OBJECTIVES

A thorough evaluation of the skin and its appendages is frequently outside the area of expertise of the neurologist who deals with neuromuscular disorders. However, the skin is more frequently affected in neuromuscular disorders and deserves more attention than so far acknowledged.

METHODS

Review of publications by searching Medline dealing with skin disorders in neuromuscular disorders.

RESULTS

Skin abnormalities are most frequently found in patients with dermatomyositis, myotonic dystrophies, mitochondrial disorders, muscular dystrophies, and neuropathies. The hairs and the sweat glands are the appendages most frequently affected in neuromuscular disorders. In myotonic dystrophies and mitochondrial disorders there are indications that the rate of skin neoplasms is increased compared with the general population.

CONCLUSIONS

Skin lesions in neuromuscular disorders are not unusual. Neurologists should be aware of the cutaneous implications of neuromuscular disorders and should take a thorough history relative to cutaneous manifestations and complete a comprehensive investigation of the skin and its appendages. If there is evidence of a dermatological problem in a neuromuscular disorder, a dermatologist should be consulted. Dermatological involvement in neuromuscular disorders may contribute to the diagnosis of neuromuscular disorders and may help to differentiate between various entities. The skin should become a focus of the neurologist as well.

When should MERRF (myoclonus epilepsy associated with ragged-red fibers) be the diagnosis?

Myoclonic epilepsy associated with ragged red fibers (MERRF) is a rare mitochondrial disorder. Diagnostic criteria for MERRF include typical manifestations of the disease: myoclonus, generalized epilepsy, cerebellar ataxia and ragged red fibers (RRF) on muscle biopsy. Clinical features of MERRF are not necessarily uniform in the early stages of the disease, and correlations between clinical manifestations and physiopathology have not been fully elucidated. It is estimated that point mutations in the tRNALys gene of the DNAmt, mainly A8344G, are responsible for almost 90% of MERRF cases. Morphological changes seen upon muscle biopsy in MERRF include a substantive proportion of RRF, muscle fibers showing a deficient activity of cytochrome c oxidase (COX) and the presence of vessels with a strong reaction for succinate dehydrogenase and COX deficiency. In this review, we discuss mainly clinical and laboratory manifestations, brain images, electrophysiological patterns, histology and molecular findings as well as some differential diagnoses and treatments.

Mitochondrial dysfunction: a neglected component of skin diseases

Aberrant mitochondrial structure and function influence tissue homeostasis and thereby contribute to multiple human disorders and ageing. Ten per cent of patients with primary mitochondrial disorders present skin manifestations that can be categorized into hair abnormalities, rashes, pigmentation abnormalities and acrocyanosis. Less attention has been paid to the fact that several disorders of the skin are linked to alterations of mitochondrial energy metabolism. This review article summarizes the contribution of mitochondrial pathology to both common and rare skin diseases. We explore the intriguing observation that a wide array of skin disorders presents with primary or secondary mitochondrial pathology and that a variety of molecular defects can cause dysfunctional mitochondria. Among them are mutations in mitochondrial- and nuclear DNA-encoded subunits and assembly factors of oxidative phosphorylation (OXPHOS) complexes; mutations in intermediate filament proteins involved in linking, moving and shaping of mitochondria; and disorders of mitochondrial DNA metabolism, fatty acid metabolism and heme synthesis. Thus, we assume that mitochondrial involvement is the rule rather than the exception in skin diseases. We conclude the article by discussing how improving mitochondrial function can be beneficial for aged skin and can be used as an adjunct therapy for certain skin disorders. Consideration of mitochondrial energy metabolism in the skin creates a new perspective for both dermatologists and experts in metabolic disease.

FGF21 in ataxia patients with spinocerebellar atrophy and mitochondrial disease

BACKGROUND

Serum fibroblast growth factor 21 (FGF21) was proven to be a useful biomarker for the presence of mitochondrial neuromuscular disease.

METHODS

In the present study, we used the difference in the serum FGF21 level to differentiate between ataxia patients with hereditary spinocerebellar atrophy (SCA-ataxia) and those with mitochondrial syndrome (Mito-ataxia). Patients with SCA-ataxia (SCA2, SCA3) and Mito-ataxia (MELAS, MERRF, LHON, maternal inherited hearing impairment mtDNA A1555G mutation) were recruited in this study. All SCA-ataxia patients revealed a consistent pattern of cerebellar atrophy. On the contrary, some of the Mito-ataxia patients exhibited a vascular lesion with cerebellar infarction.

RESULTS

Extremely higher levels of serum FGF21 were found in the Mito-ataxia patients with MERRF and MELAS diseases, but not in patients with SCA-ataxia or LHON/mtDNA A1555G mutation. The positive trend between the mtDNA heteroplasmy and serum FGF21 was indicated in either MERRF (P=0.003, r=0.923) or MELAS (P=0.070, r=0.566) patients.

CONCLUSION

Serum FGF21 can be applied as the first molecular screening among patients suspected to be victims of hereditary ataxia with neuromuscular degeneration prior to mass genetic screening.

Insights into the pathogenesis and treatment of cancer from inborn errors of metabolism

Mutations in genes that play fundamental roles in metabolic pathways have been found to also play a role in tumor development and susceptibility to cancer. At the same time, significant progress has been made in the treatment of patients with inborn errors of metabolism (IEM),(1) resulting in increased longevity and the unmasking of cancer predisposition, frequently hepatocellular carcinoma, in these conditions. These patients offer a potential opportunity to deepen our understanding of how intermediary metabolism impacts tumorigenesis. We provide an overview from the perspective of cancers in patients affected with IEM and discuss how dysregulation of these specific metabolic pathways might contribute to the mechanisms of cancer development and treatment.

Insights into the pathogenesis and treatment of cancer from inborn errors of metabolism

Mutations in genes that play fundamental roles in metabolic pathways have been found to also play a role in tumor development and susceptibility to cancer. At the same time, significant progress has been made in the treatment of patients with inborn errors of metabolism (IEM),(1) resulting in increased longevity and the unmasking of cancer predisposition, frequently hepatocellular carcinoma, in these conditions. These patients offer a potential opportunity to deepen our understanding of how intermediary metabolism impacts tumorigenesis. We provide an overview from the perspective of cancers in patients affected with IEM and discuss how dysregulation of these specific metabolic pathways might contribute to the mechanisms of cancer development and treatment.

Mitochondrial ataxias

Mitochondrial disorders (MIDs) are an increasingly recognized condition. The second most frequently affected organ in MIDs is the central nervous system. One of the most prevalent clinical CNS manifestations of MIDs is ataxia. Ataxia may be even the dominant manifestation of a MID. This is why certain MIDs should be included in the classification of heredoataxias or at least considered as differentials of classical heredoataxias. MIDs due to mutations of the mitochondrial DNA, which develop ataxia include the MERRF, NARP, MILS, or KSS syndrome. More rarely, ataxia may be a feature of MELAS, LHON, PS, MIDD, or MSL. MIDs due to mutations of the nuclear DNA, which develop ataxia include LS, SANDO, SCAE, AHS, XSLA/A, IOSCA, MIRAS, MEMSA, or LBSL syndrome. More rarely ataxia can be found in AD-CPEO, AR-CPEO, MNGIE, DIDMOAD, CoQ-deficiency, ADOAD, DCMA, or PDC-deficiency. MIDs most frequently associated with ataxia are the non-syndromic MIDs. Syndromic and non-syndromic MIDs with ataxia should be delineated from classical heredoataxias to initiate appropriate symptomatic or supportive treatment.