GPIBD12

Hyperphosphatasia with Mental Retardation Syndrome 6

Clinical Characteristics
Ocular Features: 

Congenital cataracts may be present.  The eyes appear deeply-set and strabismus has been seen in severely affected cases.   

Systemic Features: 

Two families have been reported.  The range of severity in symptoms is wide.  Birth may occur prematurely especially in the presence of polyhydramnios.  Postnatal development can be complicated by seizures, chronic lung disease, developmental regression, and renal disease.  Poor growth secondary to feeding difficulties have been reported.  Death can occur in early childhood.

Dysmorphic features include a short neck, bitemporal narrowing, depressed nasal bridge, and proximal limb shortening.  Osteopenia, flexion contractures, and hip dysplasia may be present.  Dilatation of the renal collecting system with increased echogenicity have been reported.  Creatine kinase and serum alkaline phosphatase may be increased and muscle histology shows small, atrophic fibers with increased fibrosis and considerable variations in fiber size.

Genetics

Homozygous mutations in the PIGY gene (4q22.1) resulting in deficiencies of glycosylphosphatidylinositol synthesis have been associated with this condition.  

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No effective treatment has been reported.

References
Article Title: 

Mutations in PIGY: expanding the phenotype of inherited glycosylphosphatidylinositol deficiencies

Ilkovski B, Pagnamenta AT, O'Grady GL, Kinoshita T, Howard MF, Lek M, Thomas B, Turner A, Christodoulou J, Sillence D, Knight SJ, Popitsch N, Keays DA, Anzilotti C, Goriely A, Waddell LB, Brilot F, North KN, Kanzawa N, Macarthur DG, Taylor JC, Kini U, Murakami Y, Clarke NF. Mutations in PIGY: expanding the phenotype of inherited glycosylphosphatidylinositol deficiencies. Hum Mol Genet. 2015 Nov 1;24(21):6146-59.

PubMed ID: 
26293662
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