Clinical Description
The phenotypic spectrum of CHCHD10-related disorders is broad and can include any of the following alone or in any combination: mitochondrial myopathy, amyotrophic lateral sclerosis, frontotemporal dementia (FTD), late-onset spinal motor neuronopathy, and axonal Charcot-Marie-Tooth neuropathy. Cerebellar ataxia may also be found in combination with these disorders, but not as the sole neurologic manifestation.
To date, approximately 100 individuals have been identified with a pathogenic variant in CHCHD10 [Bannwarth et al 2014, Ajroud-Driss et al 2015, Auranen et al 2015, Penttilä et al 2015]. The following description of the phenotypes associated with this condition is based on these reports. It should be noted that other individuals have been reported with CHCHD10 variants for which the pathogenicity is controversial and there is a need for more studies to classify them as pathogenic or not [Tazelaar et al 2018].
Mitochondrial myopathy may present with exercise intolerance; proximal, axial, and/or facial muscle weakness; ptosis; and amyotrophy. Deafness may also be observed.
Early onset. In a Puerto Rican family, affected individuals had myopathy (appearing in the first decade of life) and short stature [
Ajroud-Driss et al 2015].
Late onset. In a French family, affected individuals had late-onset myopathy with motor neuron disease, FTD, and cerebellar ataxia [
Bannwarth et al 2014].
Amyotrophic lateral sclerosis
(ALS).
CHCHD10-related ALS and ALS of other causes (see ALS Overview) are clinically indistinguishable, including in male-to-female ratio, age of onset, symptom distribution, and severity of disease. Most individuals with CHCHD10-related ALS meet El Escorial criteria for ALS [Brooks et al 2000] and have both UMN and LMN involvement. Within a family, clinical variability is considerable, especially regarding age of onset and longevity.
The ALS may occur by itself or in combination with FTD (referred to as FTD-ALS).
Onset. Mean age of onset is 53 years (age range 25-75 years). Upper limb involvement is more frequent at onset of ALS phenotype; bulbar involvement is more predominant at onset in the FTD-ALS phenotype.
Progression. Bulbar dysfunction (atrophy of facial and masticatory muscles, perioral fasciculations, and severe dysphagia leading to frequent aspiration) become prominent in the final stages of the disease. Affected individuals eventually develop respiratory failure, which is the main cause of death. Mean disease duration prior to death is 8.6 years (range 2-17 years).
Frontotemporal dementia (FTD) is a presenile dementia affecting the frontal and temporal cortex and some subcortical nuclei. Clinical presentation is variable. Affected individuals may have slowly progressive behavioral changes, cognitive decline with language disturbance, and/or extrapyramidal signs.
Onset and duration of disease. In individuals with CHCHD10-related FTD, symptoms start between ages 50 and 67 years. Disease duration is usually between four and 27 years.
Behavioral changes. Disinhibition and loss of initiative are the most common presenting symptoms. Affected individuals lose interest in their environment and neglect their personal hygiene. Obsessive-compulsive behavior and delusions or hallucinations are early clinical features in some. Roaming, restlessness, verbal aggressiveness, hyperorality (including alcohol abuse), and financial mismanagement are frequently seen [
Foster et al 1997,
Bird et al 1999].
Persecutory delusions and visual or auditory hallucinations, which occur rarely in FTD in general, are not reported in individuals with CHCHD10-related FTD.
Cognitive decline. Word-finding difficulties and semantic paraphasias in conversational speech are common early findings. Orientation in time and place, visuo-constructive functions, and short-term memory remain intact initially. Executive functions, attention, concentration, and abstract reasoning ability become impaired in all affected individuals. Language comprehension remains relatively preserved over the course of the disease. Perseveration, repetitive utterances, and echolalia lead to mutism after several years [
Foster et al 1997].
Extrapyramidal signs. Affected individuals may show parkinsonian signs including decreased facial expression, bradykinesia, postural instability, and rigidity without resting tremor.
Neuroimaging. Findings can include the following:
Frontal and/or temporal atrophy on brain CT or MRI
Decrease of cerebral perfusion anteriorly (single-photon emission computed tomography [SPECT])
Frontotemporal hypometabolism (positron emission tomography with 18F-fluorodeoxyglucose [FDG-PET])
Reduced striatal uptake of 18F-fluoro-L-dopa
Spinal motor neuronopathy
Spinal motor neuronopathy phenotype in CHCHD10-related disorders (also known as spinal muscular atrophy, Jokela type or SMAJ) is characterized by cramps and fasciculations, slowly progressive and predominantly lower-limb weakness, and diminished or absent deep tendon reflexes; respiratory symptoms are absent.
Onset and progression. Onset typically occurs between ages 30 and 73 years (mean age 42 years). Progression tends to be slow.
Mild, non-progressive dysphagia appears later in the disease course in 13% of affected individuals. About half of affected individuals develop mild reduction in sensory nerve amplitudes or reduced vibration sense in the distal lower limbs usually later in the disease course. Affected individuals remain ambulant for several decades after onset [
Penttilä et al 2015].
Axonal Charcot-Marie-Tooth neuropathy
Onset and progression. The onset of symptoms varies from age 30 to 56 years (mean age 44). The typical presenting symptom was slowly progressive lower leg muscle weakness, and small hand muscles were affected later on in the disease. Progression tends to be slow.
Clinical examination has consistently shown loss of tendon reflexes, muscle weakness, and atrophy. Sensory abnormalities such as loss of sensation for vibration or cold were strong enough to be detected on clinical examination in seven of 12 individuals.
No signs of upper motor neuron disease, bulbar symptoms, or progressive cognitive issues have been observed.
Muscular MRI. Lower-limb muscle MRI showed edema or fatty degeneration that was pronounced distally (particularly in calves) and milder in thighs.
Neurophysiologic findings. ENMG showed chronic motor neuropathy with regeneration; for some, sensory findings (decreased sural nerve action potential amplitude) were evident (consistent with typical CMT2 neuropathy).
Cerebellar ataxia in CHCHD10-related disorders is characterized by ataxia, dysarthria, and eventual deterioration of bulbar functions. Affected individuals have gait difficulties and slurred speech.
Onset is in the sixth decade. Individuals may first notice balance problems in going down stairs or making sudden turns. In the early stages of disease affected individuals may display brisk deep tendon reflexes, hypermetric saccades, and nystagmus [
Schmitz-Hübsch et al 2006]. Mild dysphagia, indicated by choking on food and drink, may also occur early in the disease.
Progression. As the disease progresses saccadic velocity slows and upgaze palsy develops. Nystagmus often disappears with evolving saccadic abnormalities.
As the ataxia worsens, other cerebellar signs such as dysmetria, dysdiadochokinesia, and hypotonia become apparent.
Genotype-Phenotype Correlations
No genotype-phenotype correlations have been identified.
The clinical course of CHCHD10-related disorders is highly variable, even within a family, and is not predictable from the type or location of the pathogenic variant.
Prevalence
The prevalence of CHCHD10-related disorders is not known at present.
CHCHD10 pathogenic variants have been identified in individuals from different geographic regions including America, Asia, and Europe.