Background and aim To describe the clinical and genetic characteristics of a mother and her son presenting with two distinct and rare forms of retinal degeneration.

Methods Investigations in both patients comprised spectral domain optical coherence tomography (SD-OCT), fundus autofluorescence imaging, non-contact biometry, ultrasonography, electroretinography (ERG) and analysis of the mutational status of the KCNV2 and MFRP genes in genomic DNA.

Results The clinical course and typical ERG pattern indicated a ‘cone dystrophy with supernormal rod electroretinogram’ in the proband, and SD-OCT demonstrated a subfoveal optical gap with loss of the inner segment/outer segment junction line. The proband was homozygous for a c.782C>A (p.Ala261Asp) mutation in KCNV2. Her son's axial length was shortened with refractive errors of +16.75 dioptres in the right and +14.0 dioptres in the left eye; ERG evidenced a rod–cone dystrophy, OCT showed central macular thickening with cystoid changes and ultrasonography revealed optic disc drusen. MFRP analysis disclosed a 1 bp deletion (c.498delC) that predicts a truncated protein.

Conclusions Two distinct ocular phenotypes with pathogenic mutations in two different genes segregated in this family. The coexistence of two independent autosomal recessive disorders should be considered even when dealing with diseases that bear low carrier frequencies in the general population.