Retinopathy with Neutropenia
Defective Genes
Clinical Characteristics
Ocular Features
Pigmentary retinopathy was reported in a 25 year old female with moderately reduced visual acuity. Rare bone spicules pigment deposits were present in the periphery and macular edema was noted. Severely reduced scotopic and photopic responses were recorded.
Systemic Features
The single reported individual had congenital neutropenia and microcephaly. She had evident growth retardation and microcephaly at birth with subsequent recurrent upper respiratory infections and gingivitis. Speech and motor development were normal. Short stature was noted as well. The limbs were described as slender as in Cohen syndrome (216550) but no truncal obesity or joint hypermobility was present. The facial dysmorphism only vaguely resembled that found in Cohen syndrome (216550).
Genetics
Inheritance
This is a newly described condition whose unique identity remains to be established since only a single patient has been reported. This patient carried two heterozygous splicing mutations in the same VPS13B gene, the same gene in which more than 100 homozygous mutations have been found in individuals with Cohen syndrome (216550). Each parent carried a different splicing mutation in VPS13B.
Cohen syndrome (216550) however, has additional phenotypic features such as truncal obesity, intellectual disabilities, intermittent neutropenia, microcephaly, facial dysmorphism, myopia, and progressive chorioretinal dystrophy. Variable amounts of neutropenia were observed from age 5 years but the marrow was normocellular in appearance.
Isolated retinopathy with neutropenia may or may not be an autosomal recessive variant of Cohen syndrome (216550).
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.