Post-artificial-menopause syndrome
Post-polio syndrome
Postcholecystectomy syndrome
Postgastrectomy syndromes
Postinfectious thrombocytopenia 
Postpartum hypopituitarism
Postpartum panhypopituitary syndrome
Post-traumatic stress disorder
Post-traumatic syndrome
Postural hypotension
Pre-excitation syndrome
Precocious puberty
Preeclampsia
Pregnancy loss
Pregnancy-induced hypertension
Premature atrial contraction (PAC)
Premature atrial tachycardia
Premature beats/contraction, atrial
Premature beats/contraction, ventricular
Premature ejaculation
Premature gray hair
Premature ventricular contraction (PVC)
Premenstrual syndrome
Premenstrual tension syndrome
Prepubescent vulvovaginitis
Presenile dementia (Alzheimer's)
Pressure ulcer
Priapism
Prickle cell carcinoma
Prickly heat
Primary adrenocortical insufficiency
Primary biliary cirrhosis (PBC)
Primary glaucoma
Primary hemorrhagic thrombocythemia
Primary nocturnal enuresis
Primary polycythemia
Proctitis, radiation
Proctocolitis, idiopathic
Progressive external ophthalmoplegia
Progressive myopia
Progressive systemic sclerosis
Prolapse of anal canal
Prolapse of gastric mucosa
Prolapse of uterus
Prostate cancer
Prostatic hyperplasia, benign (BPH)
Prostatitis
Protein-losing gastroenteropathy
Pruritus
Pruritus ani
Pruritus scroti
Pruritus vulvae
Pseudohypertrophic muscular dystrophy
Psoriasis
Psychogenic anorgasmy
Ptosis of eyelid
Ptyalism
Puerperal bleeding
Puerperal pyrexia
Pull
Pulmonary tuberculosis
Pulpitis
Pulseless disease
Pure red cell aplasia
Purpura, allergic
Purpura, idiopathic thrombocytopenic
Pyelectasis
Pyelonephritis
Pyoderma
Pyopneumothorax/Pyothorax