polyneuropathy

Spastic Paraplegia 78

Clinical Characteristics
Ocular Features: 

Reduced upgaze with nystagmus and strabismus have been reported.  

Systemic Features: 

This progressive neurodegenerative disorder usually has its onset in young adults but the signs and symptoms are highly variable.  Ambulation and gait difficulties combined with spasticity and lower limb weakness are common signs.  Ataxia and dysarthria are also important signs.  Some individuals have dementia while others have only mild cognitive impairment.  Some individuals have mild signs of Parkinsonism.

Brain imaging may show cerebellar and cortical atrophy with a thin corpus callosum. 

Genetics

This condition results from homozygous or compound heterozygous mutations in the ATP13A2 gene (1p36.13).

The same gene is also mutated in the Kufor-Rakeb syndrome (606693), an early-onset form of Parkinsonism.  

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Loss-of-function mutations in the ATP13A2/PARK9 gene cause complicated hereditary spastic paraplegia (SPG78)

Estrada-Cuzcano A, Martin S, Chamova T, Synofzik M, Timmann D, Holemans T, Andreeva A, Reichbauer J, De Rycke R, Chang DI, van Veen S, Samuel J, Schols L, Poppel T, Mollerup Sorensen D, Asselbergh B, Klein C, Zuchner S, Jordanova A, Vangheluwe P, Tournev I, Schule R. Loss-of-function mutations in the ATP13A2/PARK9 gene cause complicated hereditary spastic paraplegia (SPG78). Brain. 2017 Feb;140(Pt 2):287-305.

PubMed ID: 
28137957

Genetic and phenotypic characterization of complex hereditary spastic paraplegia

Kara E, Tucci A, Manzoni C, Lynch DS, Elpidorou M, Bettencourt C, Chelban V, Manole A, Hamed SA, Haridy NA, Federoff M, Preza E, Hughes D, Pittman A, Jaunmuktane Z, Brandner S, Xiromerisiou G, Wiethoff S, Schottlaender L, Proukakis C, Morris H, Warner T, Bhatia KP, Korlipara LV, Singleton AB, Hardy J, Wood NW, Lewis PA, Houlden H. Genetic and phenotypic characterization of complex hereditary spastic paraplegia. Brain. 2016 Jul;139(Pt 7):1904-18.

PubMed ID: 
27217339

Mitochondrial DNA Depletion Syndrome 1

Clinical Characteristics
Ocular Features: 

Progressive external ophthalmoplegia has an adult onset, usually in the late second or early third decade of life.  Ptosis is commonly present as well.

Systemic Features: 

This condition has been called a mitochondrial neurogastrointestinal encephalopathy (MNGIE).  Gastrointestinal problems are among the most disabling with poor absorption of foodstuffs leading to weight loss, marked cachexia, and chronic malnutrition.  Added to this are gastroparesis, constipation, vomiting, and intermittent diarrhea with abdominal pain.  Many individuals develop diverticulosis and diverticulitis that may lead to intestinal perforations.  The combined intestinal dysfunctions can lead to signs of intestinal pseudoobstruction.

Many patients have a progressive sensorineural hearing loss.  Leukoencephalopathy, sensorimotor peripheral neuropathy, and sometimes mild proximal limb weakness may be present.

Genetics

Homozygous and compound heterozygous mutations in the TYMP gene (22q13.33) are responsible for this autosomal recessive disorder.  This nuclear gene is active in the maintainence of mitochondrial DNA.  When the gene is dysfunctional, the mitochondria can be depleted to a variable extent and they may contain multiple deletions and point mutations.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is no effective treatment for the overall condition.  Nutritionists can provide important advice on diet to maintain good nutrition.  Regular monitoring by gastroenterologists is important.  Perforations of the bowels require prompt surgical repair.  

References
Article Title: 

Mitochondrial neurogastrointestinal encephalomyopathy: an autosomal recessive disorder due to thymidine phosphorylase mutations

Nishino I, Spinazzola A, Papadimitriou A, Hammans S, Steiner I, Hahn CD, Connolly AM, Verloes A, Guimaraes J, Maillard I, Hamano H, Donati MA, Semrad CE, Russell JA, Andreu AL, Hadjigeorgiou GM, Vu TH, Tadesse S, Nygaard TG, Nonaka I, Hirano I, Bonilla E, Rowland LP, DiMauro S, Hirano M. Mitochondrial neurogastrointestinal encephalomyopathy: an autosomal recessive disorder due to thymidine phosphorylase mutations. Ann Neurol. 2000 Jun;47(6):792-800.

PubMed ID: 
10852545

Ataxia with Oculomotor Apraxia 4

Clinical Characteristics
Ocular Features: 

Oculomotor apraxia is usually noted after the ataxia and dystonia are apparent.

Systemic Features: 

The mean age of first symptoms is 4.3 years with dystonia being the first symptom.  Cerebellar ataxia is usually the second symptom to appear.  Cognitive impairment is present in most but not all patients with this condition.  This can progress to severe dementia in some individuals.  Dystonia may become attenuated with time.  Peripheral neuropathy with decreased vibration sense and areflexia is often present.  Cerebellar atrophy is present in all patients.

Motor difficulties such as weakness and muscle atrophy may lead to loss of independent mobility by the second to third decades.

Genetics

Homozygous or compound heterozygous mutations in the PNKP gene (19q13.33) are responsible for this disorder.

Mutations in this gene have also been associated with an infantile form of epileptic encephalopathy, microcephaly, and developmental delay (613402).

See also Ataxia with Oculomotor Apraxia 1 (208920) with hypoalbuminemia, Ataxia with Oculomotor Apraxia 2 (606002), and Ataxia with Oculomotor Apraxia 3 (615217).

Pedigree: 
Autosomal dominant
Treatment
Treatment Options: 

There is no general treatment for this condition but physical therapy may be helpful in the early stages.

References
Article Title: 

Refsum Disease, Adult

Clinical Characteristics
Ocular Features: 

A retinitis pigmentosa-like retinopathy is the major ocular manifestation of this disease.  There is typical night blindness and visual field constriction.   Rod ERG responses are usually subnormal.  However, central acuity is also reduced due to a degenerative maculopathy.   Cataracts and optic atrophy are common.  The macula may undergo progressive degeneration and optic atrophy is not uncommon.  Some patients have defective pupillary responses.

Systemic Features: 

Onset of symptoms is usually late in the first decade and sometimes into the third decade.  There is usually a polyneuropathy with impaired motor reflexes and paresis in the limbs.  A progressive sensorineural hearing loss occurs in many patients.  Sensory deficits also occur.  Some have ataxia and skin changes of ichthyosis.  Anosmia is a near universal feature.  Heart failure may occur and cardiac abnormalities such as conduction defects can occur.  A variety of skeletal abnormalities such as pes cavus, short fourth metatarsals, and evidence of epiphyseal dysplasia have been reported.  There is considerable clinical heterogeneity even within families.

Phytanic acid oxidase activity as measured in fibroblasts is often low while serum phytanic acid is increased.  The cerebrospinal fluid contains increased protein but no increase in cells.

Genetics

This disorder results from mutations in the PHYH (PAHX) gene (10pter-p11.2) encoding phytanoyl-CoA hydroxylase, or, more rarely in PEX7 (6q22-q24) encoding peroxin-7 resulting in an uncommon condition (10% of cases) sometimes called adult Refsum disease-2. 

Mutations in the latter gene also cause rhizomelic chondrodysplasia punctata type 1 (215100) which does not have all of the neurological features or the retinopathy.

There is also so-called infantile form of Refsum disease (266510).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

A diet low in phytanic acid can lead to improvement in the neurologic symptoms such as the ataxia and polyneuropathy but must be instituted in early stages of the disease.  This approach may not be as beneficial for the visual or auditory symptoms.

References
Article Title: 
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