OMIM ID:
Retinitis Pigmentosa with Ataxia
Alternate Names
Defective Genes
Clinical Characteristics
Ocular Features
Pigmentary retinopathy has been noted by 6 months of age. Typical symptoms of retinitis pigmentosa are reported by early childhood. The visual fields are progressively constricted and a ring scotoma can be plotted. Night blindness and visual acuity loss are evident in the first decade of life and progressively worsen leading to severe handicaps by the third. Fundus pigmentation in the midperiphery becomes more prominent and in at least some patients the pattern consists of typical bone spicules. Cellophane maculopathy has been described.
Systemic Features
Proprioceptive deficits and areflexia appear in early childhood and ataxia worsens as individuals mature. Scoliosis and general weakness and wasting become prominent manifestations. Sensory neuropathy with loss of vibratory and position sense, astereognosia, and agraphesthesia can become apparent in the first decade of life. Walking is delayed and gait abnormalities are clearly evident by the second decade leading to orthopedic deformities such as scoliosis. Unassisted walking becomes impossible. The intrinsic hand and foot muscles also have mild weakness. Sural nerve biopsy may reveal loss of large myelinated fibers. Hyperintense signals in the posterior spinal columns can be seen on MRI. No anatomic changes have been described in the cerebrum or cerebellum.
Genetics
Inheritance
This is an autosomal recessive disorder resulting from homozygous mutations in FLVCR1 (1q32.2-q41). This disorder has some clinical similarities to Biemond 1 syndrome but differs in the inheritance pattern and the molecular basis.
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.