Hypotonia, Infantile, with Psychomotor Retardation
Patient Information
Characteristics
Background and History
This rare hereditary disorder has so far been reported in only two families in the Middle East. It is primarily manifest in neurological and muscular problems.
Clinical Correlations
Fetal (in utero) movements are decreased and at birth infants are floppy (hypotonia). From birth they require tube feeding and respiratory assistance due to breathing problems. Neurological development is slow. Imaging of the brain reveals a variety of malformations in most patients. The heart may have developmental defects as well. Biopsies of skeletal muscle shows a number of abnormalities. A defect in one of the nerves that supplies a muscle that moves the eye results in crossing of the eyes (strabismus).
Genetics
Inheritance
This condition is inherited in an autosomal recessive pattern due to the presence of a gene change in both members of a specific pair. Parents with a single mutation are clinically normal but when both parents carry the change each of their children have a 25% risk of inheriting this condition.
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.
Diagnosis and Prognosis
The extreme weakness of infants is a clue to this condition. Pediatricians and neurologists are likely to cooperate in the diagnosis which needs to be confirmed by a gene test. Infants with this disorder may not live beyond 6 months of age although rare individuals can live for several years with the aid of intensive supportive care. No treatment is available for the general condition.
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