OMIM ID:
Hypotonia, Infantile, with Psychomotor Retardation And Characteristic Facies 1
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Nystagmus, strabismus and sometimes optic atrophy have been noted. Poor fixation may be present.
Systemic Features
This progressive disorder can be evident at birth based on the facial dysmorphism. The face is triangular, the forehead is prominent, the nose is small, the ears appear large and low-set. The mouth appears wide with a thin upper lip. Early development may be near normal for the first 6 months but thereafter psychomotor regression and slow physical growth are evident. Patients have microcephaly and seldom achieve normal milestones. Spasticity in the extremities and truncal hypotonia with distal muscle atrophy are evident. The face appears triangular, the forehead is prominent, the nose is small, and the ears appear large and low-set. Pectus carinatum and pes varus may be present. Males often have cryptorchidism.
Brain imaging has revealed cerebellar atrophy and “while matter abnormalities”. Sural nerve biopsies show evidence of infantile neuroaxonal dystrophy.
Some individuals are less severely affected, retain the ability to speak, and are able to walk at least into the second decade of life.
Genetics
Inheritance
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.