Pathognomonic is a sign or symptom that is so characteristic of a disease that it makes the diagnosis. Pathognomonic (pronounced patho-no-monic) comes from the Greek “pathognomonikos” meaning “skilled in judging diseases.” As it is very important to know how to assess characteristic manifestations of some communicable diseases at an early stage, here are the pathognomonic signs and symptoms of some common communicable diseases.

• AIDS — opportunistic and malignant manifestations, T4 below 200/dl. (Opportunistic infection - infection that occurs because of a weakened immune system. Opportunistic infections are a particular danger for people with AIDS. The HIV virus itself does not cause death, but the opportunistic infections that occur because of its effect on the immune system can.)
• Amoebiasis — bloody mucoid stool.
• Ascariasis — vomiting, passing out of worm.
• Candidiasis — cheeselike discharge.
• Chicken pox — vesiculopopular lesions.
• Cholera — rice-watery stool.
• Dengue/Hemorrhagic Fever — Herman’s sign. It appears on the upper and lower extremities, purplish or violaceous red with blanched areas about 1 cm or less in size.
• Diptheria — pseudomembrane, a localized inflammatory process; Grayish-white, leathery consistency.
• Enterobiasis — nocturnal itchiness.
• Filariasis - Elephantiasis.
• German Measles/Rubella — Forscheimer’s spots, a mild enanthem of petechial lesions.
• Gonorrhea — thick purulent discharge.
• Herpes Zoster — lesions follow peripheral nerve pathway.
• Leptospirosis — orange eyes.
• Malaria — fever and chills.
• Measles/Rubeola — Koplik’s spots, little spots inside the mouth. The spots look like a tiny grains of white sand, each surrounded by a red ring. They are found especially on the inside of the cheek (the buccal mucosa) opposite the 1st and 2nd upper molars.
• Meningitis — nucchal rigidity.
• Mumps — swollen parotid glands.
• Pertussis — paroxysmal coughs ending with whoop.
• Pneumonia — rusty sputum.
• Polio — flaccid paralysis, weakness or paralysis and reduced muscle tone without other obvious cause (e.g., trauma).
• Rabies — hydrophobia, a morbid fear of water. Because of this name, many people think that rabies makes one afraid of water. In fact, this is not the case (although rabies does cause mental confusion of other kinds). The name hydrophobia comes from the fact that animals and people with rabies get spasms in their throat muscles that are so painful that they cannot eat or drink, and so will refuse water in spite of being very thirsty.
• Scabies — weeping itch.
• Scarlet Fever — raspberry tongue.
• Syphilis — painless chancre or ulceration.
• Tetanus — locked jaw or trismus.
• Tuberculosis — initially ASYMPTOMATIC.
• Typhoid Fever — 3 cardinal signs: ladderlike fever, rose spots, spleenomegaly (enlargement of spleen beyond its normal size).