Retinitis pigmentosa

Retinitis pigmentosa is a feature of all except

a.) Refsum's disease

b.) Hallavardian Spatz

c.) NARP

d.) Abetaglobulinemia

Retinitis pigmentosa is seen in a variety of diseases, so the differential of this sign alone, is broad.

RP combined with deafness (congenital or progressive) is called Usher syndrome.

RP combined with opthalmoplegia, dysphagia, ataxia, and cardiac conduction defects is seen in the mitochondrial DNA disorder Kearns-Sayre syndrome (aka Ragged Red Fiber Myopathy)

RP combined with retardation, peripheral neuropathy, acanthotic (spiked) RBCs, ataxia, steatorrhea, is absence of VLDL is seen inabetalipoproteinemia.

Other conditions include neurosyphilis, toxoplasmosis , abetalipoproteinemia, and Refsum's disease.