cardiac disease

Microphthalmia and Anophthalmia, ALDH1A3 Associated

Clinical Characteristics
Ocular Features: 

Patients have a variety of ocular malformations including microphthalmia and clinical anophthalmia.  Some have orbital cysts. Imaging may reveal hypoplastic optic nerves and chiasms.

Systemic Features: 

Both cardiac (pulmonary stenosis and septal defects) and neurological deficits (autism spectrum disorders and 'intellectual disability') have been reported.  Birth weight and head circumference are often low.  However, brain imaging has revealed no consistent malformations.

Genetics

This is an autosomal recessive disorder resulting from homozygous mutations in the gene ALDH1A3 (15q26.3) which encodes the enzyme retinaldehyde dehydrogenase.  Mutations in ALDH1A3 impair the enzymatic oxidation of retinaldehyde important to the synthesis of retinoic acid, a key signaling molecule in eye development. 

However, mutations in other genes important to ocular development such as GJA3 and SOX2 (a transcription factor) may result in a similar phenotype.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment for the ocular problems is available.

References
Article Title: 

ALDH1A3 Mutations Cause Recessive Anophthalmia and Microphthalmia

Fares-Taie L, Gerber S, Chassaing N, Clayton-Smith J, Hanein S, Silva E, Serey M, Serre V, G?(c)rard X, Baumann C, Plessis G, Demeer B, Br?(c)tillon L, Bole C, Nitschke P, Munnich A, Lyonnet S, Calvas P, Kaplan J, Ragge N, Rozet JM. ALDH1A3 Mutations Cause Recessive Anophthalmia and Microphthalmia. Am J Hum Genet. 2013 Feb 7;92(2):265-70.

PubMed ID: 
23312594

Hunter Syndrome (MPS II)

Clinical Characteristics
Ocular Features: 

Corneal clouding may be noted as early as 6 months of age but is usually absent. When present it is milder than in some other forms of mucopolysaccharidosis.  A pigmentary retinopathy with variable severity is often present.  The disc may be elevated and appears swollen.  Secondary optic atrophy may be seen in long standing cases.

Systemic Features: 

Mild to severe developmental delays are common and mental retardation has been reported in some cases.  There is often 'pebbling' of the skin over the neck and chest.  Joint stiffness, short stature, and skeletal deformities are common.   Many have short necks, a protuberant abdomen, a broad chest, and facial coarseness.  Hepatosplenomegaly, hearing loss, hernias, and carpal tunnel syndrome are often present.  The skull is large with a J-shaped sella, the vertebral bodies are hypoplastic anteriorly, the pelvis and femoral heads are hypoplastic and the diaphyses are expanded.

A severe form, type A, has its onset in the first two to four years of life, with more rapid progression and death commonly by adolescence.  Many patients have obstructive pulmonary disease and heart failure.  The IDS deficiency is similar to that of type B which is less severe and compatible with life into the 7th decade.  Intelligence is often normal in type B.

Genetics

Hunter syndrome, or MPS II, is one of seven lysosomal enzyme deficiencies responsible for the degradation of mucopolysaccharides, and the only one known to be X-linked (Xq28).  The mutation in IDS leads to a deficiency of iduronate sulfatase resulting in accumulation of dermatan and heparin sulfate.  Rare affected females may have chromosomal deletions instead of a simple mutation in IDS.

Pedigree: 
X-linked recessive, carrier mother
X-linked recessive, father affected
Treatment
Treatment Options: 

Various therapies are under development including enzyme replacement, gene transfers, and bone marrow transplantation.  Human iduronate-2-sulfatase (Idursulfase) has been used with encouraging signs but it is too early to determine the long term effectiveness.

References
Article Title: 
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