Clinical Characteristics
Ocular Features
This disorder is generally considered to consist of simple displacement of the pupil and dislocation of the lens (usually in opposite directions). However, other abnormalities are often present such as persistent pupillary membrane (87%), iridohyaloid adhesions, increased corneal thickness, enlarged corneal diameters, and axial myopia. The iris may transilluminate (67%) and the pupils dilate poorly. Iridodenesis is common (85%). The lens is often malformed and in some cases frankly microspherophakic. The lens displacement can progress and cataracts seem to form at a relatively young age. Visual acuity is highly variable, ranging from 20/20 to light perception depending upon the density of cataracts which often develop at a relatively young age. Prominent iris processes into the anterior chamber angle have been reported and glaucoma, both acute and chronic, is sometimes seen. Retinal detachment is a risk.
Studies in families with ectopia lentis et papillae have revealed that as many as 50% of individuals with dislocated lenses do not have ectopic pupils.
Systemic Features
None reported
Genetics
Inheritance
This disorder is usually inherited in an autosomal recessive pattern. Multiple affected sibs have been born to consanquineous matings. However, other families in which detailed ophthalmological examinations were done have suggested dominant inheritance based upon the presence of more subtle ocular signs in relatives. This is likely a more clinically heterogeneous disorder than has been appreciated.
In five Norwegian families a homozygous 20 bp deletion has been found in the gene ADAMTSL4 on chromosome 1 (c.767_786del20) (1q21.3) producing a frameshift and the introduction of a stop codon leading to truncation of the protein product. Mutations in the same gene have also been found in the autosomal recessive form of isolated ectopia lentis (225100).
Pedigree
Autosomal recessive
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.
In order for autosomal recessive disorders to be expressed, offspring generally must inherit two mutations, one from each carrier parent. Carriers with only one mutation, such as the parents, do not have clinical disease. Note that carrier parents can expect that 1 in 4 children (25%) will inherit both mutations and have the disorder, 2 in 4 children (50%) will be carriers like their parents, while 1 in 4 children (25%) inherit neither mutation.