Mitochondrial complex 5 (ATP synthase) deficiency, nuclear type 6(MC5DN6)

MedGen UID:: 1684729
•Concept ID:: C5231461
•: Disease or Syndrome

Synonym:	MITOCHONDRIAL COMPLEX V (ATP SYNTHASE) DEFICIENCY, NUCLEAR TYPE 6

Gene (location): Gene(s) directly associated with this condition or phenotype.	ATP5MK (10q24.33)

Monarch Initiative:	MONDO:0032869
OMIM®:	618683

Definition

Mitochondrial complex V (ATP synthase) deficiency nuclear type 6 (MC5DN6) is an autosomal recessive progressive and degenerative disorder characterized by episodic regression of gross motor skills beginning in early childhood. The episodes are associated with metabolic stress, including fever, illness, and general anesthesia. Patients develop gait difficulties or loss of ambulation, as well as other variable abnormalities, including abnormal movements, hemiplegia, and persistent lethargy. Brain imaging shows degenerative features in the basal ganglia and brainstem consistent with a diagnosis of Leigh syndrome (see 256000) (summary by Barca et al., 2018). For a discussion of genetic heterogeneity of mitochondrial complex V deficiency, see MC5DN1 (604273). [from OMIM]

Clinical features

From HPO

Hypertrophic cardiomyopathy

MedGen UID:: 2881
•Concept ID:: C0007194
•: Disease or Syndrome

Hypertrophic cardiomyopathy (HCM) is defined by the presence of increased ventricular wall thickness or mass in the absence of loading conditions (hypertension, valve disease) sufficient to cause the observed abnormality.

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Cerebellar ataxia

MedGen UID:: 849
•Concept ID:: C0007758
•: Disease or Syndrome

Cerebellar ataxia refers to ataxia due to dysfunction of the cerebellum. This causes a variety of elementary neurological deficits including asynergy (lack of coordination between muscles, limbs and joints), dysmetria (lack of ability to judge distances that can lead to under- or overshoot in grasping movements), and dysdiadochokinesia (inability to perform rapid movements requiring antagonizing muscle groups to be switched on and off repeatedly).

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Chorea

MedGen UID:: 3420
•Concept ID:: C0008489
•: Disease or Syndrome

Chorea (Greek for 'dance') refers to widespread arrhythmic involuntary movements of a forcible, jerky and restless fashion. It is a random-appearing sequence of one or more discrete involuntary movements or movement fragments. Movements appear random because of variability in timing, duration or location. Each movement may have a distinct start and end. However, movements may be strung together and thus may appear to flow randomly from one muscle group to another. Chorea can involve the trunk, neck, face, tongue, and extremities.

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Lethargy

MedGen UID:: 7310
•Concept ID:: C0023380
•: Sign or Symptom

A state of fatigue, either physical or mental slowness and sluggishness, with difficulties in initiating or performing simple tasks. Distinguished from apathy which implies indifference and a lack of desire or interest in the task. A person with lethargy may have the desire, but not the energy to engage in personal or socially relevant tasks.

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Hyperreflexia

MedGen UID:: 57738
•Concept ID:: C0151889
•: Finding

Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles.

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Bradykinesia

MedGen UID:: 115925
•Concept ID:: C0233565
•: Sign or Symptom

Bradykinesia literally means slow movement, and is used clinically to denote a slowness in the execution of movement (in contrast to hypokinesia, which is used to refer to slowness in the initiation of movement).

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Developmental regression