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Multiple mitochondrial dysfunctions syndrome 7(MMDS7)

MedGen UID:
1841222
Concept ID:
C5830586
Disease or Syndrome
Synonym: MMDS7
 
Gene (location): GCSH (16q23.2)
 
Monarch Initiative: MONDO:0957382
OMIM®: 620423

Definition

Mitochondrial dysfunctions syndrome-7 (MMDS7) is an autosomal recessive disorder characterized by a clinical spectrum ranging from neonatal fatal glycine encephalopathy to an attenuated phenotype of developmental delay, behavioral problems, limited epilepsy, and variable movement problems (Arribas-Carreira et al., 2023). For a general description and a discussion of genetic heterogeneity of multiple mitochondrial dysfunctions syndrome, see MMDS1 (605711). [from OMIM]

Clinical features

From HPO
Recurrent singultus
MedGen UID:
893074
Concept ID:
C0744897
Finding
A contraction of the diaphragm that repeats several times per minute. In humans, the abrupt rush of air into the lungs causes the epiglottis to close, creating a hic sound. Also known as synchronous diaphragmatic flutter (SDF), or singultus, from the Latin singult, the act of catching one's breath while sobbing. The hiccup is an involuntary action involving a reflex arc.
Ankle clonus
MedGen UID:
68672
Concept ID:
C0238651
Finding
Clonus is an involuntary tendon reflex that causes repeated flexion and extension of the foot. Ankle clonus is tested by rapidly flexing the foot upward.
Partial atrioventricular canal
MedGen UID:
868879
Concept ID:
C4023290
Congenital Abnormality
A specific combination of heart defects including a primum atrial septal defect and cleft anterior mitral valve leaflet. There is not an inlet ventricular septal defect present. There are two valve annuluses and two valve orifices.
Feeding difficulties
MedGen UID:
65429
Concept ID:
C0232466
Finding
Impaired ability to eat related to problems gathering food and getting ready to suck, chew, or swallow it.
Decreased liver function
MedGen UID:
65430
Concept ID:
C0232744
Finding
Reduced ability of the liver to perform its functions.
Poor suck
MedGen UID:
324693
Concept ID:
C1837142
Finding
An inadequate sucking reflex, resulting in the difficult of newborns to be breast-fed.
Coma
MedGen UID:
1054
Concept ID:
C0009421
Disease or Syndrome
The complete absence of wakefulness and consciousness, which is evident through a lack of response to any form of external stimuli.
Dystonic disorder
MedGen UID:
3940
Concept ID:
C0013421
Sign or Symptom
An abnormally increased muscular tone that causes fixed abnormal postures. There is a slow, intermittent twisting motion that leads to exaggerated turning and posture of the extremities and trunk.
Hallucinations
MedGen UID:
6709
Concept ID:
C0018524
Mental or Behavioral Dysfunction
Perceptions in a conscious and awake state that, in the absence of external stimuli, have qualities of real perception. These perceptions are vivid, substantial, and located in external objective space.
Impulsivity
MedGen UID:
43850
Concept ID:
C0021125
Mental or Behavioral Dysfunction
Acting on the spur of the moment or on a momentary basis without consideration of outcomes; having difficulty establishing or following plans; experiencing a sense of urgency and engaging in behavior that is uninhibited, cannot be inhibited, and is uncontrolled. The possibility of repression is inconceivable.
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.
Myoclonus
MedGen UID:
10234
Concept ID:
C0027066
Finding
Very brief, involuntary random muscular contractions occurring at rest, in response to sensory stimuli, or accompanying voluntary movements.
Seizure
MedGen UID:
20693
Concept ID:
C0036572
Sign or Symptom
A seizure is an intermittent abnormality of nervous system physiology characterized by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.
Agitation
MedGen UID:
88447
Concept ID:
C0085631
Sign or Symptom
A state of excessive motor activity that is associated with mental distress or a feeling of substantial unease or inner tension. Distinguished from restlessness by the increased level of emotional distress and negative intensity of the experience. Agitation has a significant level of physical activity that is typically threatening to the self or others.
Hyperreflexia
MedGen UID:
57738
Concept ID:
C0151889
Finding
Hyperreflexia is the presence of hyperactive stretch reflexes of the muscles.
Areflexia
MedGen UID:
115943
Concept ID:
C0234146
Finding
Absence of neurologic reflexes such as the knee-jerk reaction.
Hypoplasia of the corpus callosum
MedGen UID:
138005
Concept ID:
C0344482
Congenital Abnormality
Underdevelopment of the corpus callosum.
Hyperactivity
MedGen UID:
98406
Concept ID:
C0424295
Finding
Hyperactivity is a condition characterized by constant and unusually high levels of activity, even in situations where it is deemed inappropriate.
Global developmental delay
MedGen UID:
107838
Concept ID:
C0557874
Finding
A delay in the achievement of motor or mental milestones in the domains of development of a child, including motor skills, speech and language, cognitive skills, and social and emotional skills. This term should only be used to describe children younger than five years of age.
Hypsarrhythmia
MedGen UID:
195766
Concept ID:
C0684276
Finding
Hypsarrhythmia is abnormal interictal high amplitude waves and a background of irregular spikes. There is continuous (during wakefulness), high-amplitude (>200 Hz), generalized polymorphic slowing with no organized background and multifocal spikes demonstrated by electroencephalography (EEG).
Focal-onset seizure
MedGen UID:
199670
Concept ID:
C0751495
Disease or Syndrome
A focal-onset seizure is a type of seizure originating within networks limited to one hemisphere. They may be discretely localized or more widely distributed, and may originate in subcortical structures.
Autistic behavior
MedGen UID:
163547
Concept ID:
C0856975
Mental or Behavioral Dysfunction
Persistent deficits in social interaction and communication and interaction as well as a markedly restricted repertoire of activity and interest as well as repetitive patterns of behavior.
Exaggerated startle response
MedGen UID:
329357
Concept ID:
C1740801
Finding
An exaggerated startle reaction in response to a sudden unexpected visual or acoustic stimulus, or a quick movement near the face.
EEG with burst suppression
MedGen UID:
369943
Concept ID:
C1969156
Finding
The burst suppression pattern in electroencephalography refers to a characteristic periodic pattern of low voltage (<10 microvolts) suppressed background and a relatively shorter pattern of higher amplitude slow, sharp, and spiking complexes.
Irritability
MedGen UID:
397841
Concept ID:
C2700617
Mental Process
A proneness to anger, i.e., a tendency to become easily bothered or annoyed.
Multifocal seizures
MedGen UID:
482664
Concept ID:
C3281034
Finding
Seizures that start from several different areas of the brain (i.e., with multiple ictal onset locations).
Infantile spasms
MedGen UID:
854616
Concept ID:
C3887898
Disease or Syndrome
Infantile spasms represent a subset of "epileptic spasms". Infantile Spasms are epileptic spasms starting in the first year of life (infancy).
Reduced brain N-acetyl aspartate level by MRS
MedGen UID:
868367
Concept ID:
C4022761
Finding
A decrease in the level of N-acetyl aspartate in the brain identified by magnetic resonance spectroscopy (MRS).
Elevated brain lactate level by MRS
MedGen UID:
868368
Concept ID:
C4022762
Finding
An increase in the level of lactate in the brain identified by magnetic resonance spectroscopy (MRS).
Myoclonic seizure
MedGen UID:
1385980
Concept ID:
C4317123
Sign or Symptom
A myoclonic seizure is a type of motor seizure characterized by sudden, brief (<100 ms) involuntary single or multiple contraction of muscles or muscle groups of variable topography (axial, proximal limb, distal). Myoclonus is less regularly repetitive and less sustained than is clonus.
Increased CSF glycine concentration
MedGen UID:
1691638
Concept ID:
C5139615
Finding
Abnormally increased levels of glycine in cerebrospinal fluid.
Abnormal diffusion weighted cerebral MRI morphology
MedGen UID:
1716407
Concept ID:
C5397636
Finding
A diffusion abnormality observed in diffusion-weighted magnetic resonance imaging (MRI) of the brain. Molecular diffusion refers to the notion that any type of molecule in a fluid (eg, water) is randomly displaced as the molecule is agitated by thermal energy. Restricted diffusion of water appears bright on diffusion-weighted images.
Thin corpus callosum
MedGen UID:
1785336
Concept ID:
C5441562
Anatomical Abnormality
An abnormally thin corpus callous, due to atrophy, hypoplasia or agenesis. This term is intended to be used in situations where it is not known if thinning of the corpus callosum (for instance, as visualized by magnetic resonance tomography) is due to abnormal development (e.g. a leukodystrophy) or atrophy following normal development (e.g. neurodegeneration).
Elevated brain glycine level by MRS
MedGen UID:
1842032
Concept ID:
C5826743
Finding
An increase in the level of glycine in the brain identified by magnetic resonance spectroscopy (MRS).
Thrombocytopenia
MedGen UID:
52737
Concept ID:
C0040034
Disease or Syndrome
A reduction in the number of circulating thrombocytes.
Hypertonia
MedGen UID:
10132
Concept ID:
C0026826
Finding
A condition in which there is increased muscle tone so that arms or legs, for example, are stiff and difficult to move.
Hypotonia
MedGen UID:
10133
Concept ID:
C0026827
Finding
Hypotonia is an abnormally low muscle tone (the amount of tension or resistance to movement in a muscle). Even when relaxed, muscles have a continuous and passive partial contraction which provides some resistance to passive stretching. Hypotonia thus manifests as diminished resistance to passive stretching. Hypotonia is not the same as muscle weakness, although the two conditions can co-exist.
Dolichocephaly
MedGen UID:
65142
Concept ID:
C0221358
Congenital Abnormality
An abnormality of skull shape characterized by a increased anterior-posterior diameter, i.e., an increased antero-posterior dimension of the skull. Cephalic index less than 76%. Alternatively, an apparently increased antero-posterior length of the head compared to width. Often due to premature closure of the sagittal suture.
Secondary microcephaly
MedGen UID:
608952
Concept ID:
C0431352
Finding
Head circumference which falls below 2 standard deviations below the mean for age and gender because of insufficient head growth after birth.
Axial hypotonia
MedGen UID:
342959
Concept ID:
C1853743
Finding
Muscular hypotonia (abnormally low muscle tone) affecting the musculature of the trunk.
Apnea
MedGen UID:
2009
Concept ID:
C0003578
Sign or Symptom
Lack of breathing with no movement of the respiratory muscles and no exchange of air in the lungs. This term refers to a disposition to have recurrent episodes of apnea rather than to a single event.
Respiratory failure requiring assisted ventilation
MedGen UID:
870821
Concept ID:
C4025279
Finding
A state of respiratory distress that requires a life saving intervention in the form of gaining airway access and instituting positive pressure ventilation.
Hyperglycemia
MedGen UID:
5689
Concept ID:
C0020456
Disease or Syndrome
An increased concentration of glucose in the blood.
Hypernatremia
MedGen UID:
6966
Concept ID:
C0020488
Disease or Syndrome
An abnormally increased sodium concentration in the blood.
Hypoglycemia
MedGen UID:
6979
Concept ID:
C0020615
Disease or Syndrome
A decreased concentration of glucose in the blood.
Metabolic acidosis
MedGen UID:
65117
Concept ID:
C0220981
Pathologic Function
Metabolic acidosis (MA) is characterized by a fall in blood pH due to a reduction of serum bicarbonate concentration. This can occur as a result of either the accumulation of acids (high anion gap MA) or the loss of bicarbonate from the gastrointestinal tract or the kidney (hyperchloremic MA). By definition, MA is not due to a respirary cause.
Hyperglycinemia
MedGen UID:
82817
Concept ID:
C0268559
Disease or Syndrome
An elevated concentration of glycine in the blood.
Open mouth
MedGen UID:
116104
Concept ID:
C0240379
Finding
A facial appearance characterized by a permanently or nearly permanently opened mouth.
Gingival overgrowth
MedGen UID:
87712
Concept ID:
C0376480
Finding
Hyperplasia of the gingiva (that is, a thickening of the soft tissue overlying the alveolar ridge. The degree of thickening ranges from involvement of the interdental papillae alone to gingival overgrowth covering the entire tooth crown.
Anteverted nares
MedGen UID:
326648
Concept ID:
C1840077
Finding
Anteriorly-facing nostrils viewed with the head in the Frankfurt horizontal and the eyes of the observer level with the eyes of the subject. This gives the appearance of an upturned nose (upturned nasal tip).
Cyanosis
MedGen UID:
1189
Concept ID:
C0010520
Sign or Symptom
Bluish discoloration of the skin and mucosa due to poor circulation or inadequate oxygenation of arterial or capillary blood.

Recent clinical studies

Etiology

Alfadhel M, Nashabat M, Alrifai MT, Alshaalan H, Al Mutairi F, Al-Shahrani SA, Plecko B, Almass R, Alsagob M, Almutairi FB, Al-Rumayyan A, Al-Twaijri W, Al-Owain M, Taylor RW, Kaya N
Eur J Paediatr Neurol 2018 Jan;22(1):46-55. Epub 2017 Oct 16 doi: 10.1016/j.ejpn.2017.10.003. PMID: 29122497

Diagnosis

Alfadhel M, Nashabat M, Alrifai MT, Alshaalan H, Al Mutairi F, Al-Shahrani SA, Plecko B, Almass R, Alsagob M, Almutairi FB, Al-Rumayyan A, Al-Twaijri W, Al-Owain M, Taylor RW, Kaya N
Eur J Paediatr Neurol 2018 Jan;22(1):46-55. Epub 2017 Oct 16 doi: 10.1016/j.ejpn.2017.10.003. PMID: 29122497

Prognosis

Eidi M, Garshasbi M
BMC Neurol 2019 Jul 6;19(1):153. doi: 10.1186/s12883-019-1387-2. PMID: 31279336Free PMC Article
Shukla A, Hebbar M, Srivastava A, Kadavigere R, Upadhyai P, Kanthi A, Brandau O, Bielas S, Girisha KM
J Hum Genet 2017 Jul;62(7):723-727. Epub 2017 Mar 30 doi: 10.1038/jhg.2017.35. PMID: 28356563Free PMC Article

Clinical prediction guides

Eidi M, Garshasbi M
BMC Neurol 2019 Jul 6;19(1):153. doi: 10.1186/s12883-019-1387-2. PMID: 31279336Free PMC Article
Shukla A, Hebbar M, Srivastava A, Kadavigere R, Upadhyai P, Kanthi A, Brandau O, Bielas S, Girisha KM
J Hum Genet 2017 Jul;62(7):723-727. Epub 2017 Mar 30 doi: 10.1038/jhg.2017.35. PMID: 28356563Free PMC Article

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