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Developmental and epileptic encephalopathy, 66(EIEE66; DEE66)

MedGen UID:
1648486
Concept ID:
C4748070
Disease or Syndrome
Synonym: EPILEPTIC ENCEPHALOPATHY, EARLY INFANTILE, 66
 
Gene (location): PACS2 (14q32.33)
 
Monarch Initiative: MONDO:0054845
OMIM®: 618067

Definition

Developmental and epileptic encephalopathy-66 (DEE66) is a neurologic disorder characterized by the onset of various types of seizures in the first days or weeks of life. Most seizures have focal origins; secondary generalization is common. Seizure control is difficult at first, but may become easier with time. Affected individuals show global developmental delay with hypotonia, behavioral abnormalities, and dysmorphic features or ophthalmologic defects. Brain imaging often shows cerebellar dysgenesis. A subset of patients have extraneurologic manifestations, including hematologic and distal limb abnormalities (summary by Olson et al., 2018). For a general phenotypic description and a discussion of genetic heterogeneity of DEE, see 308350. [from OMIM]

Clinical features

From HPO
Cryptorchidism
MedGen UID:
8192
Concept ID:
C0010417
Congenital Abnormality
Cryptorchidism, or failure of testicular descent, is a common human congenital abnormality with a multifactorial etiology that likely reflects the involvement of endocrine, environmental, and hereditary factors. Cryptorchidism can result in infertility and increases risk for testicular tumors. Testicular descent from abdomen to scrotum occurs in 2 distinct phases: the transabdominal phase and the inguinoscrotal phase (summary by Gorlov et al., 2002).
Clinodactyly of the 5th finger
MedGen UID:
340456
Concept ID:
C1850049
Congenital Abnormality
Clinodactyly refers to a bending or curvature of the fifth finger in the radial direction (i.e., towards the 4th finger).
Dextrocardia
MedGen UID:
4255
Concept ID:
C0011813
Congenital Abnormality
The heart is located in the right hand sided hemithorax. That is, there is a left-right reversal (or "mirror reflection") of the anatomical location of the heart in which the heart is locate on the right side instead of the left.
Atrial septal defect
MedGen UID:
6753
Concept ID:
C0018817
Congenital Abnormality
Atrial septal defect (ASD) is a congenital abnormality of the interatrial septum that enables blood flow between the left and right atria via the interatrial septum.
Ventricular septal defect
MedGen UID:
42366
Concept ID:
C0018818
Congenital Abnormality
A hole between the two bottom chambers (ventricles) of the heart. The defect is centered around the most superior aspect of the ventricular septum.
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.
Status epilepticus
MedGen UID:
11586
Concept ID:
C0038220
Disease or Syndrome
Status epilepticus is a type of prolonged seizure resulting either from the failure of the mechanisms responsible for seizure termination or from the initiation of mechanisms which lead to abnormally prolonged seizures (after time point t1). It is a condition that can have long-term consequences (after time point t2), including neuronal death, neuronal injury, and alteration of neuronal networks, depending on the type and duration of seizures.
Motor stereotypies
MedGen UID:
21318
Concept ID:
C0038271
Individual Behavior
Use of the same abnormal action in response to certain triggers or at random. They may be used as a way to regulate one's internal state but must otherwise have no apparent functional purpose.
Clonic seizure
MedGen UID:
66708
Concept ID:
C0234535
Disease or Syndrome
A clonic seizure is a type of motor seizure characterized by sustained rhythmic jerking, that is regularly repetitive.
Delayed ability to walk
MedGen UID:
66034
Concept ID:
C0241726
Finding
A failure to achieve the ability to walk at an appropriate developmental stage. Most children learn to walk in a series of stages, and learn to walk short distances independently between 12 and 15 months.
Tonic seizure
MedGen UID:
82855
Concept ID:
C0270844
Disease or Syndrome
A tonic seizure is a type of motor seizure characterized by unilateral or bilateral limb stiffening or elevation, often with neck stiffening.
Delayed speech and language development
MedGen UID:
105318
Concept ID:
C0454644
Finding
A degree of language development that is significantly below the norm for a child of a specified age.
Bilateral tonic-clonic seizure
MedGen UID:
141670
Concept ID:
C0494475
Sign or Symptom
A bilateral tonic-clonic seizure is a seizure defined by a tonic (bilateral increased tone, lasting seconds to minutes) and then a clonic (bilateral sustained rhythmic jerking) phase.
Epileptic encephalopathy
MedGen UID:
452596
Concept ID:
C0543888
Disease or Syndrome
A condition in which epileptiform abnormalities are believed to contribute to the progressive disturbance in cerebral function. Epileptic encephalaopathy is characterized by (1) electrographic EEG paroxysmal activity that is often aggressive, (2) seizures that are usually multiform and intractable, (3) cognitive, behavioral and neurological deficits that may be relentless, and (4) sometimes early death.
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.
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.
Focal clonic seizure
MedGen UID:
155749
Concept ID:
C0752323
Disease or Syndrome
A focal clonic seizure is a type of focal motor seizure characterized by sustained rhythmic jerking, that is regularly repetitive.
Focal tonic seizure
MedGen UID:
199867
Concept ID:
C0752324
Disease or Syndrome
A type of focal motor seizure characterized by sustained increase in muscle contraction, lasting a few seconds to minutes.
Broad-based gait
MedGen UID:
167799
Concept ID:
C0856863
Finding
An abnormal gait pattern in which persons stand and walk with their feet spaced widely apart. This is often a component of cerebellar ataxia.
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.
Bilateral tonic-clonic seizure with focal onset
MedGen UID:
164077
Concept ID:
C0877017
Disease or Syndrome
A bilateral tonic-clonic seizure with focal onset is a focal-onset seizure which progresses into a bilateral tonic-clonic phase.
Generalized tonic seizure
MedGen UID:
322935
Concept ID:
C1836508
Disease or Syndrome
A generalized tonic seizure is a type of generalized motor seizure characterized by bilateral limb stiffening or elevation, often with neck stiffening without a subsequent clonic phase. The tonic activity can be a sustained abnormal posture, either in extension or flexion, sometimes accompanied by tremor of the extremities.
Cerebellar vermis hypoplasia
MedGen UID:
333548
Concept ID:
C1840379
Finding
Underdevelopment of the vermis of cerebellum.
Intellectual disability
MedGen UID:
811461
Concept ID:
C3714756
Mental or Behavioral Dysfunction
Intellectual disability, previously referred to as mental retardation, is characterized by subnormal intellectual functioning that occurs during the developmental period. It is defined by an IQ score below 70.
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.
Anemia
MedGen UID:
1526
Concept ID:
C0002871
Disease or Syndrome
A reduction in erythrocytes volume or hemoglobin concentration.
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.
Enlarged cisterna magna
MedGen UID:
344031
Concept ID:
C1853377
Finding
Increase in size of the cisterna magna, one of three principal openings in the subarachnoid space between the arachnoid and pia mater, located between the cerebellum and the dorsal surface of the medulla oblongata.
Neutropenia
MedGen UID:
163121
Concept ID:
C0853697
Finding
An abnormally low number of neutrophils in the peripheral blood.
Wide mouth
MedGen UID:
44238
Concept ID:
C0024433
Congenital Abnormality
Distance between the oral commissures more than 2 SD above the mean. Alternatively, an apparently increased width of the oral aperture (subjective).
Downslanted palpebral fissures
MedGen UID:
98391
Concept ID:
C0423110
Finding
The palpebral fissure inclination is more than two standard deviations below the mean.
Macrodontia of permanent maxillary central incisor
MedGen UID:
371973
Concept ID:
C1835095
Finding
Increased size of the maxillary central secondary incisor tooth.
Widely spaced teeth
MedGen UID:
337093
Concept ID:
C1844813
Finding
Increased spaces (diastemata) between most of the teeth in the same dental arch.
Coarse facial features
MedGen UID:
335284
Concept ID:
C1845847
Finding
Absence of fine and sharp appearance of brows, nose, lips, mouth, and chin, usually because of rounded and heavy features or thickened skin with or without thickening of subcutaneous and bony tissues.
Wide nasal bridge
MedGen UID:
341441
Concept ID:
C1849367
Finding
Increased breadth of the nasal bridge (and with it, the nasal root).
Everted lower lip vermilion
MedGen UID:
344003
Concept ID:
C1853246
Finding
An abnormal configuration of the lower lip such that it is turned outward i.e., everted, with the Inner aspect of the lower lip vermilion (normally opposing the teeth) being visible in a frontal view.
Thin upper lip vermilion
MedGen UID:
355352
Concept ID:
C1865017
Finding
Height of the vermilion of the upper lip in the midline more than 2 SD below the mean. Alternatively, an apparently reduced height of the vermilion of the upper lip in the frontal view (subjective).
Downturned corners of mouth
MedGen UID:
356471
Concept ID:
C1866195
Anatomical Abnormality
A morphological abnormality of the mouth in which the angle of the mouth is downturned. The oral commissures are positioned inferior to the midline labial fissure.
Synophrys
MedGen UID:
98132
Concept ID:
C0431447
Congenital Abnormality
Meeting of the medial eyebrows in the midline.
Astigmatism
MedGen UID:
2473
Concept ID:
C0004106
Disease or Syndrome
Astigmatism (from the Greek 'a' meaning absence and 'stigma' meaning point) is a condition in which the parallel rays of light entering the eye through the refractive media are not focused on a single point. Both corneal and noncorneal factors contribute to refractive astigmatism. Corneal astigmatism is mainly the result of an aspheric anterior surface of the cornea, which can be measured readily by means of a keratometer; in a small fraction of cases (approximately 1 in 10) the effect is neutralized by the back surface. The curvature of the back surface of the cornea is not considered in most studies, because it is more difficult to measure; moreover, in the case of severe corneal astigmatism, there is evidence that both surfaces have the same configuration. Noncorneal factors are errors in the curvature of the 2 surfaces of the crystalline lens, irregularity in the refractive index of the lens, and an eccentric lens position. Since the cornea is the dominant component of the eye's refracting system, a highly astigmatic cornea is likely to result in a similarly astigmatic ocular refraction (summary by Clementi et al., 1998).
Hypermetropia
MedGen UID:
43780
Concept ID:
C0020490
Disease or Syndrome
An abnormality of refraction characterized by the ability to see objects in the distance clearly, while objects nearby appear blurry.
Hypertelorism
MedGen UID:
9373
Concept ID:
C0020534
Finding
Although hypertelorism means an excessive distance between any paired organs (e.g., the nipples), the use of the word has come to be confined to ocular hypertelorism. Hypertelorism occurs as an isolated feature and is also a feature of many syndromes, e.g., Opitz G syndrome (see 300000), Greig cephalopolysyndactyly (175700), and Noonan syndrome (163950) (summary by Cohen et al., 1995).
Myopia
MedGen UID:
44558
Concept ID:
C0027092
Disease or Syndrome
Nearsightedness, also known as myopia, is an eye condition that causes blurry distance vision. People who are nearsighted have more trouble seeing things that are far away (such as when driving) than things that are close up (such as when reading or using a computer). If it is not treated with corrective lenses or surgery, nearsightedness can lead to squinting, eyestrain, headaches, and significant visual impairment.\n\nNearsightedness usually begins in childhood or adolescence. It tends to worsen with age until adulthood, when it may stop getting worse (stabilize). In some people, nearsightedness improves in later adulthood.\n\nFor normal vision, light passes through the clear cornea at the front of the eye and is focused by the lens onto the surface of the retina, which is the lining of the back of the eye that contains light-sensing cells. People who are nearsighted typically have eyeballs that are too long from front to back. As a result, light entering the eye is focused too far forward, in front of the retina instead of on its surface. It is this change that causes distant objects to appear blurry. The longer the eyeball is, the farther forward light rays will be focused and the more severely nearsighted a person will be.\n\nNearsightedness is measured by how powerful a lens must be to correct it. The standard unit of lens power is called a diopter. Negative (minus) powered lenses are used to correct nearsightedness. The more severe a person's nearsightedness, the larger the number of diopters required for correction. In an individual with nearsightedness, one eye may be more nearsighted than the other.\n\nEye doctors often refer to nearsightedness less than -5 or -6 diopters as "common myopia." Nearsightedness of -6 diopters or more is commonly called "high myopia." This distinction is important because high myopia increases a person's risk of developing other eye problems that can lead to permanent vision loss or blindness. These problems include tearing and detachment of the retina, clouding of the lens (cataract), and an eye disease called glaucoma that is usually related to increased pressure within the eye. The risk of these other eye problems increases with the severity of the nearsightedness. The term "pathological myopia" is used to describe cases in which high myopia leads to tissue damage within the eye.
Nystagmus
MedGen UID:
45166
Concept ID:
C0028738
Disease or Syndrome
Rhythmic, involuntary oscillations of one or both eyes related to abnormality in fixation, conjugate gaze, or vestibular mechanisms.
Strabismus
MedGen UID:
21337
Concept ID:
C0038379
Disease or Syndrome
A misalignment of the eyes so that the visual axes deviate from bifoveal fixation. The classification of strabismus may be based on a number of features including the relative position of the eyes, whether the deviation is latent or manifest, intermittent or constant, concomitant or otherwise and according to the age of onset and the relevance of any associated refractive error.

Professional guidelines

PubMed

Vetri L, Calì F, Saccone S, Vinci M, Chiavetta NV, Carotenuto M, Roccella M, Costanza C, Elia M
Int J Mol Sci 2024 Jan 17;25(2) doi: 10.3390/ijms25021146. PMID: 38256219Free PMC Article
Harvey S, Allen NM, King MD, Lynch B, Lynch SA, O'Regan M, O'Rourke D, Shahwan A, Webb D, Gorman KM; Irish Paediatric Neurology Group
Dev Med Child Neurol 2022 Jun;64(6):780-788. Epub 2022 Jan 29 doi: 10.1111/dmcn.15153. PMID: 35092693Free PMC Article
Herzberg EM, Machie M, Glass HC, Shellhaas RA, Wusthoff CJ, Chang T, Abend NS, Chu CJ, Cilio MR, Bonifacio SL, Massey SL, McCulloch CE, Soul JS; Neonatal Seizure Registry study group
J Pediatr 2022 Mar;242:121-128.e1. Epub 2021 Nov 13 doi: 10.1016/j.jpeds.2021.11.012. PMID: 34780777

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