A 24-year-old man presents with progressive night blindness and restricted peripheral vision. Fundoscopy reveals the characteristic findings of retinitis pigmentosa. The structure marked **A** in the diagram—bone-spicule pigment clumps in the mid-periphery—represents which pathological process?
A. Hypertrophic response of retinal astrocytes to photoreceptor loss
B. Accumulation of lipofuscin within Müller glial cells due to impaired autophagy
C. Deposition of drusen-like material at the retinal pigment epithelium-Bruch membrane interface
D. Migration of retinal pigment epithelial cells into the neurosensory retina following photoreceptor degeneration
Explanation
Why Migration of retinal pigment epithelial cells into the neurosensory retina following photoreceptor degeneration is right
The bone-spicule pigment clumps (marked A) are a hallmark of retinitis pigmentosa and represent migration of melanin-laden retinal pigment epithelial (RPE) cells into the neurosensory retina. This occurs as a reactive response to progressive rod and cone photoreceptor death. The characteristic radial orientation along retinal vessels reflects the migration pathway along blood vessels. According to Kanski Clinical Ophthalmology, these pigment clumps are pathognomonic for rod–cone dystrophies and indicate the underlying degenerative process affecting the photoreceptor-RPE complex.
Why each distractor is wrong
Accumulation of lipofuscin within Müller glial cells due to impaired autophagy: While autophagy dysfunction does occur in retinitis pigmentosa, lipofuscin accumulation is intracellular and not visible as discrete pigment clumps on fundoscopy. Lipofuscin appears as diffuse retinal discoloration, not the characteristic bone-spicule pattern.
Hypertrophic response of retinal astrocytes to photoreceptor loss: Astrocytic gliosis does occur in RP but does not produce the visible pigmented clumps seen on fundoscopy. Gliosis is a microscopic finding and does not account for the melanin-based pigmentation visible clinically.
Deposition of drusen-like material at the retinal pigment epithelium-Bruch membrane interface: Drusen are characteristic of age-related macular degeneration, not retinitis pigmentosa. They are composed of lipid and protein, not melanin, and do not form the radial bone-spicule pattern seen in RP.
High-YieldNEET PG
Bone-spicule pigment clumps in retinitis pigmentosa = RPE cell migration into neurosensory retina following photoreceptor degeneration; always radially oriented along vessels.
