renal dysplasia

Mental Retardation, X-Linked 99, Syndromic, Female-Restricted

Clinical Characteristics
Ocular Features: 

Palpebral fissures are generally shortened and may slant up or down.  Cataracts of unknown morphology have been reported and strabismus is common.

Systemic Features: 

The systemic phenotype is highly variable.  Skull and facial anomalies are common with brachycephaly, bitemporal narrowing, and a broad low nasal bridge. There is general developmental delay in both motor and cognitive abilities.  Patients are short in stature while scoliosis, hip dysplasia, and post-axial polydactyly may be present.  The teeth may be malformed and numerous (29%) of individuals have hypertrichosis.  Nearly a third of individuals have a cleft palate/bifid uvula.   Heart malformations, primarily atrial septal defects, are found in about half of affected individuals and urogenital anomalies such as renal dysplasia are relatively common.  Feeding difficulties have been reported while anal atresia is present in about half of patients.   

Brain imaging reveals hypoplasia of the corpus callosum, enlarged ventricles, Dandy-Walker malformations, cerebellar hypoplasia, and abnormal gyration patterns in the frontal lobe.  Generalized hypotonia has been diagnosed in half of reported patients and seizures occur in 24%.

Genetics

This female-restricted syndrome is caused by heterozygous mutations in the USP9X gene (Xp11.4).  X-chromosome inactivation is skewed greater than 90% in the majority of females but the degree of skewing in one study was independent of clinical severity.  The majority of cases occur de novo.

In males, hemizygous mutations in the USP9X gene (300919) cause a somewhat similar disorder (MRX99) without the majority of the congenital malformations having mainly the intellectual disabilities, hypotonia, and behavioral problems.

Pedigree: 
X-linked dominant, mother affected
Treatment
Treatment Options: 

There is no known treatment for the general disorder but individual anomalies or defects such as atrial septal defects, cleft palate, and anal atresia might be surgically corrected.

References
Article Title: 

De Novo Loss-of-Function Mutations in USP9X Cause a Female-Specific Recognizable Syndrome with Developmental Delay and Congenital Malformations

Reijnders MR, Zachariadis V, Latour B, Jolly L, Mancini GM, Pfundt R, Wu KM, van Ravenswaaij-Arts CM, Veenstra-Knol HE, Anderlid BM, Wood SA, Cheung SW, Barnicoat A, Probst F, Magoulas P, Brooks AS, Malmgren H, Harila-Saari A, Marcelis CM, Vreeburg M, Hobson E, Sutton VR, Stark Z, Vogt J, Cooper N, Lim JY, Price S, Lai AH, Domingo D, Reversade B; DDD Study, Gecz J, Gilissen C, Brunner HG, Kini U, Roepman R, Nordgren A, Kleefstra T. De Novo Loss-of-Function Mutations in USP9X Cause a Female-Specific Recognizable Syndrome with Developmental Delay and Congenital Malformations. Am J Hum Genet. 2016 Feb 4;98(2):373-81.

PubMed ID: 
26833328

Short-Rib Thoracic Dysplasia 9

Clinical Characteristics
Ocular Features: 

A pigmentary retinopathy resembling retinitis pigmentosa is present in the majority of individuals.  Reduced acuity is likely responsible for the associated nystagmus and occasional strabismus.  Night blindness is a feature although the age of onset is unknown.  Visual acuity is decreased in the first decade but at least one patient at age 40 years still had vision of 20/40-20/50.  The ERG shows decreased scotopic and photopic responses as early as 12 years of age.  The retinopathy has been described as an atypical nonpigmented retinal degeneration in the peripheral retina. However, bone-spicule pigmentary deposits have been noted.  The retinal disease is progressive. 

Systemic Features: 

The LFT140 mutation has widespread effects, impacting the kidney, liver and skeletal systems.  The thorax is shortened, while the ribs are abnormally short and may result in respiratory difficulties, recurrent infections, and an early demise.  The middle phalanges of the hands and feet often have cone-shaped epiphyses, especially notable in childhood and leading to brachydactyly.  The long bones are often shortened as well.  The femoral neck can be short while the femoral epiphyses are often flattened.  Microcephaly has been reported in several individuals.

The liver may be enlarged and become fibrotic.  The kidneys often are cystic and histologically may have sclerosing glomerulonephropathy.  Kidney disease has an onset in the first decade and its progression often defines the survival prognosis.  Renal transplantation can be lifesaving when nephronophthisis develops.  Psychomotor delays have been reported but are uncommon. 

Genetics

Homozygous or compound heterozygous mutations in the IFT140 gene (16p13.3) have been identified.  However, there is some genetic heterogeneity since several patients having the typical phenotype have been reported with only heterozygous mutations.

This may be the same condition as Retinitis Pigmentosa 80 (617781) in which the same mutation occurs. 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is no treatment for the general disease.  Renal and pulmonary function needs to be monitored with intervention as needed.  Some patients have benefitted from renal transplantation.

References
Article Title: 

Combined NGS approaches identify mutations in the intraflagellar transport gene IFT140 in skeletal ciliopathies with early progressive kidney Disease

Schmidts M, Frank V, Eisenberger T, Al Turki S, Bizet AA, Antony D, Rix S, Decker C, Bachmann N, Bald M, Vinke T, Toenshoff B, Di Donato N, Neuhann T, Hartley JL, Maher ER, Bogdanovic R, Peco-Antic A, Mache C, Hurles ME, Joksic I, Guc-Scekic M, Dobricic J, Brankovic-Magic M, Bolz HJ, Pazour GJ, Beales PL, Scambler PJ, Saunier S, Mitchison HM, Bergmann C. Combined NGS approaches identify mutations in the intraflagellar transport gene IFT140 in skeletal ciliopathies with early progressive kidney Disease. Hum Mutat. 2013 May;34(5):714-24.

PubMed ID: 
23418020

Mainzer-Saldino syndrome is a ciliopathy caused by IFT140 mutations

Perrault I, Saunier S, Hanein S, Filhol E, Bizet AA, Collins F, Salih MA, Gerber S, Delphin N, Bigot K, Orssaud C, Silva E, Baudouin V, Oud MM, Shannon N, Le Merrer M, Roche O, Pietrement C, Goumid J, Baumann C, Bole-Feysot C, Nitschke P, Zahrate M, Beales P, Arts HH, Munnich A, Kaplan J, Antignac C, Cormier-Daire V, Rozet JM. Mainzer-Saldino syndrome is a ciliopathy caused by IFT140 mutations. Am J Hum Genet. 2012 May 4;90(5):864-70.

PubMed ID: 
22503633
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