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Squalene synthase deficiency(SQSD)

MedGen UID:
1648421
Concept ID:
C4748427
Disease or Syndrome
Synonym: NEURODEVELOPMENTAL DISORDER WITH LOW CHOLESTEROL AND ABNORMAL URINE ORGANIC ACIDS
 
Gene (location): FDFT1 (8p23.1)
 
Monarch Initiative: MONDO:0032566
OMIM®: 618156

Disease characteristics

Excerpted from the GeneReview: Squalene Synthase Deficiency
Squalene synthase deficiency (SQSD) is a rare inborn error of cholesterol biosynthesis with multisystem clinical manifestations similar to Smith-Lemli-Optiz syndrome. Key clinical features include facial dysmorphism, a generalized seizure disorder presenting in the neonatal period, nonspecific structural brain malformations, cortical visual impairment, optic nerve hypoplasia, profound developmental delay / intellectual disability, dry skin with photosensitivity, and genital malformations in males. [from GeneReviews]
Authors:
David Coman  |  Lisenka Vissers  |  Hans Waterham, et. al.   view full author information

Additional description

From OMIM
Squalene synthase deficiency (SQSD) is an autosomal recessive disorder characterized by profound developmental delay, brain abnormalities, 2/3 syndactyly of the toes, and facial dysmorphisms, as well as low total and LDL-cholesterol and abnormal urine organic acids (Coman et al., 2018).  http://www.omim.org/entry/618156

Clinical features

From HPO
Constipation
MedGen UID:
1101
Concept ID:
C0009806
Sign or Symptom
Infrequent or difficult evacuation of feces.
Fetal growth restriction
MedGen UID:
4693
Concept ID:
C0015934
Pathologic Function
An abnormal restriction of fetal growth with fetal weight below the tenth percentile for gestational age.
Micrognathia
MedGen UID:
44428
Concept ID:
C0025990
Congenital Abnormality
Developmental hypoplasia of the mandible.
Retrognathia
MedGen UID:
19766
Concept ID:
C0035353
Congenital Abnormality
An abnormality in which the mandible is mislocalised posteriorly.
Seizure
MedGen UID:
20693
Concept ID:
C0036572
Sign or Symptom
A seizure is an intermittent abnormality of nervous system physiology characterised by a transient occurrence of signs and/or symptoms due to abnormal excessive or synchronous neuronal activity in the brain.
Bicuspid aortic valve
MedGen UID:
57436
Concept ID:
C0149630
Congenital Abnormality
Aortic valve disease-2 (AOVD2) is characterized by bicuspid aortic valve (BAV) and dilation of the ascending aorta. Calcification of the valve and the aorta has been observed, and some patients exhibit coarctation of the aorta (Tan et al., 2012; Luyckx et al., 2019; Park et al., 2019). For a general phenotypic description and a discussion of genetic heterogeneity of aortic valve disease, see AOVD1 (109730).
Hypocholesterolemia
MedGen UID:
57479
Concept ID:
C0151718
Disease or Syndrome
An decreased concentration of cholesterol in the blood.
Dry skin
MedGen UID:
56250
Concept ID:
C0151908
Sign or Symptom
Skin characterized by the lack of natural or normal moisture.
Macrotia
MedGen UID:
488785
Concept ID:
C0152421
Congenital Abnormality
Median longitudinal ear length greater than two standard deviations above the mean and median ear width greater than two standard deviations above the mean (objective); or, apparent increase in length and width of the pinna (subjective).
Polymicrogyria
MedGen UID:
78605
Concept ID:
C0266464
Congenital Abnormality
Polymicrogyria is a congenital malformation of the cerebral cortex characterized by abnormal cortical layering (lamination) and an excessive number of small gyri (folds).
Optic nerve hypoplasia
MedGen UID:
137901
Concept ID:
C0338502
Disease or Syndrome
Underdevelopment of the optic nerve.
Hypoplasia of the corpus callosum
MedGen UID:
138005
Concept ID:
C0344482
Congenital Abnormality
Underdevelopment of the corpus callosum.
Cutaneous photosensitivity
MedGen UID:
87601
Concept ID:
C0349506
Pathologic Function
An increased sensitivity of the skin to light. Photosensitivity may result in a rash upon exposure to the sun (which is known as photodermatosis). Photosensitivity can be diagnosed by phototests in which light is shone on small areas of skin.
Elbow flexion contracture
MedGen UID:
98367
Concept ID:
C0409338
Acquired Abnormality
An elbow contracture that limits the ability of the elbow joint to be extended (straightened), meaning that the elbow is fixed in an flexed (bent) position.
Knee flexion contracture
MedGen UID:
98042
Concept ID:
C0409355
Finding
A bent (flexed) knee joint that cannot be straightened actively or passively.
Bilateral cryptorchidism
MedGen UID:
96568
Concept ID:
C0431663
Congenital Abnormality
Absence of both testes from the scrotum owing to failure of the testis or testes to descend through the inguinal canal to the scrotum.
Epicanthus
MedGen UID:
151862
Concept ID:
C0678230
Congenital Abnormality
Epicanthus is a condition in which a fold of skin stretches from the upper to the lower eyelid, partially covering the inner canthus. Usher (1935) noted that epicanthus is a normal finding in the fetus of all races. Epicanthus also occurs in association with hereditary ptosis (110100).
Hypospadias
MedGen UID:
163083
Concept ID:
C0848558
Congenital Abnormality
Abnormal position of urethral meatus on the ventral penile shaft (underside) characterized by displacement of the urethral meatus from the tip of the glans penis to the ventral surface of the penis, scrotum, or perineum.
Decreased LDL cholesterol concentration
MedGen UID:
776554
Concept ID:
C0853085
Finding
An decreased concentration of low-density lipoprotein cholesterol in the blood.
Slender long bone
MedGen UID:
331446
Concept ID:
C1833144
Finding
Reduced diameter of a long bone.
Depressed nasal bridge
MedGen UID:
373112
Concept ID:
C1836542
Finding
Posterior positioning of the nasal root in relation to the overall facial profile for age.
Low-set, posteriorly rotated ears
MedGen UID:
387834
Concept ID:
C1857486
Finding
Ears that are low-set and posteriorly rotated.
Failure to thrive in infancy
MedGen UID:
358083
Concept ID:
C1867873
Finding
Irritability
MedGen UID:
397841
Concept ID:
C2700617
Mental Process
A proneness to anger, i.e., a condition of being easily bothered or annoyed.
Profound global developmental delay
MedGen UID:
766364
Concept ID:
C3553450
Disease or Syndrome
A profound delay in the achievement of motor or mental milestones in the domains of development of a child.
Gastrostomy tube feeding in infancy
MedGen UID:
892362
Concept ID:
C4023342
Finding
Feeding problem necessitating gastrostomy tube feeding.
Abnormality of hair pigmentation
MedGen UID:
869743
Concept ID:
C4024172
Finding
An abnormality of hair pigmentation (color).
Cerebral visual impairment
MedGen UID:
890568
Concept ID:
C4048268
Pathologic Function
A form of loss of vision caused by damage to the visual cortex rather than a defect in the eye.
2-3 toe syndactyly
MedGen UID:
1645640
Concept ID:
C4551570
Congenital Abnormality
Syndactyly with fusion of toes two and three.
Increased circulating farnesol concentration
MedGen UID:
1756698
Concept ID:
C5421597
Finding
An elevated level of farnesol in the blood circulation.
Elevated circulating methylsuccinic acid concentration
MedGen UID:
1753480
Concept ID:
C5421640
Finding
Increased concentration of methylsuccinic acid in the blood circulation.

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