ambiguous genitalia

Pontocerebellar Hypoplasia 7

Clinical Characteristics
Ocular Features: 

The ocular phenotype has not been fully evaluated.  Optic atrophy, nystagmus, and strabismus have been reported in addition to dysmorphic periocular features such as epicanthal folds, upslanting lid fissures, and a flattened nasal bridge.  Infants frequently do not fix and follow.

Systemic Features: 

Infants may be small at birth and subsequent psychomotor development is delayed.  The ears are large and the palate is highly arched.  Hypotonia is present from birth but spasticity with hyperreflexia may also be seen.  Brain imaging may show a thin corpus callosum as well as olivopontocerebellar hypoplasia.  The ventricles are frequently enlarged.  Patients are frequently irritable with few spontaneous movements.

Genitalia can be ambiguous and are frequently assigned to the female gender because of microphallus, fused scrotum, absent testes, and absence of the uterus.  Many such infants are found to have XY karyotypes.  Infants considered male at birth may subsequently show regression of penile corporeal tissue and may have genitalia that more closely resemble the female gender.  Pelvic imaging and laparoscopy, however, may reveal a uterus, Fallopian tubes and a blind-ending vagina with no gonadal tissue even in individuals with XY karyotypes. 

Genetics

Homozygous or compound heterozygous mutations in the TOE1 gene (1p34.1) are responsible for this condition.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

Biallelic mutations in the 3' exonuclease TOE1 cause pontocerebellar hypoplasia and uncover a role in snRNA processing

Lardelli RM, Schaffer AE, Eggens VR, Zaki MS, Grainger S, Sathe S, Van Nostrand EL, Schlachetzki Z, Rosti B, Akizu N, Scott E, Silhavy JL, Heckman LD, Rosti RO, Dikoglu E, Gregor A, Guemez-Gamboa A, Musaev D, Mande R, Widjaja A, Shaw TL, Markmiller S, Marin-Valencia I, Davies JH, de Meirleir L, Kayserili H, Altunoglu U, Freckmann ML, Warwick L, Chitayat D, Blaser S, Caglayan AO, Bilguvar K, Per H, Fagerberg C, Christesen HT, Kibaek M, Aldinger KA, Manchester D, Matsumoto N, Muramatsu K, Saitsu H, Shiina M, Ogata K, Foulds N, Dobyns WB, Chi NC, Traver D, Spaccini L, Bova SM, Gabriel SB, Gunel M, Valente EM, Nassogne MC, Bennett EJ, Yeo GW, Baas F, Lykke-Andersen J, Gleeson JG. Biallelic mutations in the 3' exonuclease TOE1 cause pontocerebellar hypoplasia and uncover a role in snRNA processing. Nat Genet. 2017 Mar;49(3):457-464.

PubMed ID: 
28092684

Meckel Syndrome

Clinical Characteristics
Ocular Features: 

The ocular phenotype is highly variable.  The globe is often malformed or may be clinically absent.  Cryptophthalmos, clinical anophthalmia, and microphthalmos with sclerocornea and microcornea have been reported.  Posterior staphylomas, retinal dysplasia, partial aniridia, cataracts, and hypoplasia or absence of the optic nerve are sometimes seen.  Some patients have incompletely formed eyes with shallow anterior chambers, angle anomalies, and a persistent tunica vasculosa with lens opacification.  Histopathology may reveal thinning of the nerve fiber layer and a paucity of retinal ganglion cells.  The retina has been described as dysplastic with foci of rosette-like structures and abundant glial cells.

Systemic Features: 

Meckel or Meckel-Gruber syndrome is a clinically and genetically heterogeneous group of disorders with severe multisystem manifestations.  The triad of cystic renal disease, polydactyly (and sometimes syndactyly), and a skull malformation (usually an encephalocele) is considered characteristic of MKS.  However, these signs are variable and only about 60% of patients have all three features.  Many patients have additional signs such as malformations of the biliary tree, cleft palate (and/or lip), sloping forehead, low-set ears, short neck, low-set ears, ambiguous genitalia, and short, bowed limb bones.  Pulmonary hypoplasia is common which, together with kidney and liver disease, is responsible for the poor prognosis of most infants. 

Many clinical abnormalities resemble those present in the Smith-Lemli-Opitz syndrome (270400) and in Joubert syndrome (213300).

Genetics

Most conditions in this group are inherited in an autosomal recessive pattern.  Mutations in 9 genes have been identified as responsible for some variant of MKS in which there is a considerable range of clinical expression.  There is significant clinical overlap with Joubert syndrome and it is not surprising that at least 5 of these mutations have been identified in both conditions.  Further nosological confusion is generated by those who consider patients with the severe, lethal phenotype to have Meckel syndrome while those with milder disease are labeled Joubert syndrome, regardless of genotype.

Rare heterozygotes have been reported with isolated features such as polydactyly.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is no treatment for this syndrome.  The prognosis for life beyond infancy is poor due to the advanced dysfunction of numerous organs such as the kidney, lungs, liver and the central nervous system.

References
Article Title: 

Clinical and genetic heterogeneity in Meckel syndrome

Paavola P, Salonen R, Baumer A, Schinzel A, Boyd PA, Gould S, Meusburger H, Tenconi R, Barnicoat A, Winter R, Peltonen L. Clinical and genetic heterogeneity in Meckel syndrome. Hum Genet. 1997 Nov;101(1):88-92.

PubMed ID: 
9385376

Ablepharon-Macrostomia Syndrome

Clinical Characteristics
Ocular Features: 

The clinical features of this syndrome remain to be fully delineated.  Important ocular anomalies include malformations and sometimes absence of the upper and lower eyelids.  The eyelashes and eyebrows may be sparse or even missing.  The lid fissures, if present, may be shortened.  Deformities of the eyelids can lead to corneal exposure and secondary vision loss. 

Systemic Features: 

Other facial malformations include macrostomia which may be secondary to aberrant lip fusion.  Micrognathia has been described.  The external ears are often rudimentary, sometimes described as rosebuds.  The nasal bridge is low and the nostrils anteverted.  The zygomatic arches may be absent.  The nipples are often missing as well.  Scalp hair is sparse or even absent while the skin is dry, coarse, and often has redundant folds (cutis laxa).  Mild skin syndactyly, camptodactyly, finger contractures, and shortening of metacarpals have been noted.  The genitalia are often ambiguous and some patients have had ventral hernias.  Hearing loss can be a feature.  Growth retardation has been seen but developmental delays if present are mild.  Intelligence can be normal. 

Genetics

The majority of sibships suggest autosomal recessive inheritance although autosomal dominant inheritance has been proposed for several. One male child has been reported to have a partial deletion of chromosome 18 but other complex rearrangements were also present.

An amino acid substitution (lysine) in the basic domain of the TWIST2 gene has been found in seven families in which ablepharon-macrostomia followed an autosomal dominant pattern.  Mutations in the same TWIST2 domain but leading to substitutions of glutamine or alanine amino acids is responsible for the Barber-Say phenotype (209885).

Mutations in the TWIST2 gene may also be responsible for Setleis syndrome (227260). 

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Cosmetic surgery can correct at least some of the malformations. Vigorous effort may be required to maintain corneal surface wetting. 

References
Article Title: 

Recurrent Mutations in the Basic Domain of TWIST2 Cause Ablepharon Macrostomia and Barber-Say Syndromes

Marchegiani S, Davis T, Tessadori F, van Haaften G, Brancati F, Hoischen A, Huang H, Valkanas E, Pusey B, Schanze D, Venselaar H, Vulto-van Silfhout AT, Wolfe LA, Tifft CJ, Zerfas PM, Zambruno G, Kariminejad A, Sabbagh-Kermani F, Lee J, Tsokos MG, Lee CC, Ferraz V, da Silva EM, Stevens CA, Roche N, Bartsch O, Farndon P, Bermejo-Sanchez E, Brooks BP, Maduro V, Dallapiccola B, Ramos FJ, Chung HY, Le Caignec C, Martins F, Jacyk WK, Mazzanti L, Brunner HG, Bakkers J, Lin S, Malicdan MC, Boerkoel CF, Gahl WA, de Vries BB, van Haelst MM, Zenker M, Markello TC. Recurrent Mutations in the Basic Domain of TWIST2 Cause Ablepharon Macrostomia and Barber-Say Syndromes. Am J Hum Genet. 2015 Jul 2;97(1):99-110.

PubMed ID: 
26119818
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