Most Common Variation of Retinitis Pigmentosa
Autosomal recessive retinitis pigmentosa (RP) is the most common inheritance pattern, accounting for approximately 50-60% of all RP cases, followed by autosomal dominant RP (30-40%) and X-linked RP (5-15%).
Inheritance Pattern Distribution
The genetic heterogeneity of RP manifests in three primary inheritance patterns, with autosomal recessive being most prevalent 1:
- Autosomal recessive RP represents the majority of cases and typically presents with earlier onset and more severe phenotype compared to dominant forms 1
- Autosomal dominant RP (ADRP) accounts for 30-40% of cases, with rhodopsin gene mutations being particularly important in this subtype 2
- X-linked RP is the least common but often the most severe form 3
Clinical Phenotype Considerations
When considering "variation," the clinical presentation also varies significantly 3:
- Classic RP presents with progressive nyctalopia (night blindness), peripheral visual field constriction, and eventual central vision loss due to rod photoreceptor degeneration followed by cone degeneration 3, 1
- RP inversa is a rare variant characterized by macular involvement with central vision loss while peripheral vision remains intact, representing the opposite pattern of typical RP 4
Molecular Classification
From a molecular perspective, RP can be categorized by the functional systems affected 1:
- Photoreceptor outer segment renewal defects (including rhodopsin and peripherin/RDS gene mutations) - often associated with dominant inheritance 1
- Visual transduction cascade defects - predominantly associated with recessive phenotypes due to continuous pathway inactivation 1
- Retinol metabolism disturbances - associated with equal rod and cone involvement and retinal pigment epithelium deposits 1
Key Clinical Pitfalls
The rhodopsin gene is one of the most frequently mutated genes in ADRP, accounting for approximately 23.8% of cases in some populations 2. Specific mutations like p.L95P may be associated with distinct patterns such as predominantly inferior retinal involvement 2.
Clinicians should recognize that RP shows great variability in onset, severity, and clinical course, with most patients experiencing some degree of visual disability in childhood despite the heterogeneous presentation 3.