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TUBERCULOID LEPROSY (A Paucibacilliary Type)
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TUBERCULOID LEPROSY (TT) - A Paucibacilliary Type of H.D..
Tuberculoid (TT) leprosy appears on the extreme left of the Immunological Spectrum as that form of the disease which is most resistant. Those who have this form have a good Cell-Mediated Immunity (CMI). The key word in relation to this disease in making a diagnosis is “LOCALISED”. Because of the body’s strong CMI defences, the disease is being contained or localised either to a skin patch - generally ONE patch in the early stages, or to a nerve trunk. In TT leprosy, the body’s defences respond more intensely - often violently - to the presence of leprosy bacilli and their antigens. For this reason, there generally is a rather angry-looking, raised border to the patch, indicating an immunological battle. In fact, if one pathologically examines the skin tissue, it is clearly seen that the various tissue cells have experienced a traumatic disturbance, although no actual M.leprae may be visible. In TT, the macrophages play a significant role, aggregating at the sites of infection, engulfing (phagocytosis) the bacilli and their antigens and destroying them . In this process of cleaning up the bacterial rubbish, the macrophages, after engulfing and digesting the M.leprae, are transformed into epithelioid cells. Unilaterally, the macrophages cannot destroy M.leprae. Without the help of the “T-type” lymphocytes, the macrophage is powerless. This is what happens when there is no Cell-Mediated-Immuinty (CMI) as in lepromatous (LL) leprosy where the macrophage can ingest but can not digest M.leprae. In TT leprosy, the “T-Type” lymphocytes produce certain enzymes which assist the macrophage in its phagocytosis. Occasionally these transformed (epithelioid cells) macrophages combine to form “Giant Cells” which enhance the defence system’s action of destroying the bacilli.
When the affected tissue of a Tuberculoid patient is examined pathologically, such a skin biopsy shows collections of these epithelioid cells surrounded by many groups of lymphocytes and, occasionally “Giant Cells” can be seen in such a grouping. In the early stages of TT leprosy, such cell collections are present mainly around the appendages of the skin such as the nerves supplying the sweat and sebaceous glands, also the hair follicles. So violent may be the immune reaction in TT leprosy, that this inflammatory cell collection may be seen to spread even up to the epidermis. The margins of the lesion are the most active part of the patch which is warmer than surrounding tissue because the sweat glands have been destroyed. Also, the patch is dry because the sweat and sebaceous glands are not secreting and the absence of hair shows that the hair-follicle also has been destroyed.
Nerves in TT leprosy lesions can be seriously affected and even destroyed if the disease is not treated. Not only are the small cutaneous nerves within the patch affected, but the cutaneous nerves entering the patch may be found to be tender and enlarged. If the disease is not checked, these nerves can be destroyed. Several of the main nerve trunks supplying the area of infection also may be involved, such as the Ulnar at the elbow, the Median at the wrist, the Radial at the lateral aspect of the upper arm, the Lateral Popliteal at the back of the knee, the Posterior Tibial at the ankle and the Facial nerve on the side of the neck. When the epithelioid cells and lymphocytes infiltrate the nerves in their quest to find their prime target - the Schwann Cells of the nerve - this inflammatory process may destroy the nerves. There are times when the inflammation is so acute that the nerve is actually replaced by a caseous necrosis in which case, it may appear that, under the skin, there is a hard piece of rope or wire! Again, in relation to “TT” leprosy, remember the word “localised”, because the infection may be limited to one or a few nerves in which the destruction is rapid and complete. For this reason, Tuberculoid skin lesions may have a TOTAL sensory deficit, also resulting in COMPLETE paralysis.
Tuberculoid (TT) leprosy Clinical Manifestations :- Although TT patients may suffer horrendous paralysis, deformity and ulcerations when the disease is untreated, it is considered to be a MILD form of the disease!. Along with Lepromatous leprosy (LL) , the Tuberculoid type is one of the two “POLAR” types on the immunological spectrum. The TT lesions are LOCALISED and contained within a small area of the skin and one or two peripheral nerves. The skin smears of TT patients ordinarily are NEGATIVE for which reason it is believed that they are non-infectious and the case called a “closed” one. To determine the patient’s degree of resistance to leprosy, a Lepromin Test (serum made from killed M.leprae) is injected and, in the case of TT patients, the Lepromin Test is always positive.
CLINICAL FEATURES IN TUBERCULOID LEPROSY :-
(1) Lesions generally are on the face, lateral aspect of extremities and the buttocks
(2) Skin lesions may be single of few
(3) Lesions are asymmetrical
DESCRIPTION OF SKIN LESIONS:-
(1) Lesions are slightly or well infiltrated
(2) Patches may be hypopigmented or erythematous
(3) Margins of the patch are well defined
(4) Margins of the patch may be raised
(5) Patch may indicate a central area which is healing, but dry and rough
(6) Patch has a sensory deficit - often totally anaesthetic
(7) Patch may be small or large
(8) Patch is warm due to loss of sweating
(9) Hair may be absent or spare in lesions.
DESCRIPTION OF NERVE LESIONS:-
(1) The cutaneous nerve supplying the lesion is usually palpable
(2) Trunk nerves (one or two) supplying the lesion may be tender and enlarged
(3) The related main peripheral nerve trunks may show thickening, tenderness, abcess formation and occasionally calcification.
DESCRIPTION OD SMEAR EXAMINATION:-
(1) Skin smears taken by the regular “slit and scrape” method are usually negative
(2) Smears taken from the margin (active part) of the lesion occasionally show a few M.leprae
50% + of TT patients have bacilli in striated muscle and this is often far more than can be found in skin lesions.
LEPROMIN TEST :-
Strongly positive.
TT. LESIONS ALSO ARE CLASSIFIED AS “MINOR” AND “MAJOR” AS FOLLOWS:- -
Tuberculoid Minor:-
Lesions are slightly raised
The thickening of the lesion may be confined to its margin
The margin may have a “pebble-like” appearance
The lesion is usually flat at its centre
Tuberculoid Major:-
The entire lesion may be raised as a “plaque”
Lesion may only appear with raised (active) margins
The Centre of the Lesion may be flat and hyperpigmented
Healing signs may appear at Lesion’s Centre
Tuberculoid patients may present with such oedema and nerve compression within the endoneurium that the sheath of the nerve needs to be incised to reduce the pressure and prevent the destruction of the Schwann Cells. It is this intraneural pressure which is causing the damage, not the living leprosy bacillus which is wrongly thought to be “eating away” flesh and bone. Because of such intraneural pressure, the tiny blood vessels which supply nourishment to the nerves in the form of oxygen, are constricted, preventing the flow of blood and, therefore starving the nerve of its oxygen supply.
Where the sensory nerves are starved in this way, they are damaged and even destroyed, beginning at their extremities - perhaps the tips of fingers or toes - rendering them insensitive to injuries such as burns etc.. Where the motor nerves are similarly affected, muscular paralysis follows in the form of “dropped foot” where the lateral politeal nerve is involved; “Clawed Toes” in the case of the Posterior Tibial nerve; “Clawed Hand” in the case of the Ulnar and Median nerves; “Dropped Wrist” in the case of the Radial nerve. Ulnar nerve involvement can also result in atrophy of the Thenar and Hypothenar muscles of the hand, along with atrophy of the first dorsal interosseous muscle, manifesting a “wasting” of the muscle between the thumb and index finger. “Lagophthalmos” (eyes cannot be closed) in the case of the Facial nerve involvement etc. Where the autonomic nerves are involved, there is loss of hair (Madorosis - cutaneous nerve to hair follicle is affected); loss of sweating (cutaneous nerve to sebaceous nerve affected) ; dryness and warming of lesion (cutaneous nerve to sweat glands affected) etc. etc.. Email us for more info. at :- keithskilli@ozemail.com.au
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