See Rare Diseases by First Letter (R)
- Rabies
- Radiation Induced Brachial Plexopathy
- Radiation Induced Cancer
- Rasmussen Encephalitis
- Reactive Arthritis
- Rectal Neoplasm
- Recurrent Respiratory Papillomatosis
- Refsum Disease
- Refsum Disease, Infantile Form
- Relapsing Polychondritis
- Renal Cancer
- Renal Glycosuria
- Renal Tubular Acidosis
- Renal Tubular Acidosis, Distal, Autosomal Dominant
- Renal Tubular Dysgenesis
- Respiratory Distress Syndrome, Infant
- Restless Legs Syndrome, Susceptibility To, 6
- Reticular Dysgenesis
- Retinitis Pigmentosa
- Retinitis Pigmentosa-deafness Syndrome
- Retinoblastoma
- Retinopathy of Prematurity
- Retroperitoneal Fibrosis
- Rett Syndrome
- Revesz Syndrome
- Rhabdoid Tumor
- Rhabdomyosarcoma Alveolar
- Rhabdomyosarcoma Embryonal
- Rheumatic Fever
- Richter Syndrome
- Rickets
- Rod Myopathy
- Rothmund Thomson Syndrome
- Roussy Levy Syndrome
- Rubella
- Rubinstein-Taybi Syndrome
- Russell-Silver Syndrome