Clinical Diagnosis.—It must be remembered that leprosy is very slow in development, so that for months or even years there may be but slight indications of the disease, as an anaesthetic spot or the palsy of an orbicularis palpebrarum. One should always run over the lobes of the ears or region of the eyebrows to feel for shot-like nodules.
In the making of a diagnosis the information as to possible exposure to the disease is of first importance.
The leprous spots are at first rather oily from increased action of the sebaceous glands but subsequently become dry. In ancient times the hypersecretion of sebaceous material about the facial spots of nodular leprosy served as the basis of a test for leprosy, the suspected eruption being dashed with water. If the surface was not wetted it was a point in favor of leprosy. Of prime importance however is the pin prick for anaesthesia, which is the most important distinguishing characteristic, next to the finding of the bacilli, for a leprous spot. The anaesthesia is more marked in the center of the spot and may show dissociation of sensation. It is very important to examine for enlargement of the ulnar or great auricular and the earliest signs of a nerve leprosy may be anaesthesia and a slight contraction of the ring and little finger.
Of the general diseases, which may be confused with leprosy, we have the circumscribed form of scleroderma. Such spots however are dead white in color and are not anaesthetic. The prodromal manifestations with fever and sweatings simulate malaria. Elephantiasis and Madura foot have been confused with leprosy but the marked tendency to limitation to the lower extremities and absence of anaesthesia should differentiate. Probably the most difficult disease to differentiate from leprosy is syringomyelia. Morvan’s disease is only a form of syringomyelia in which the neuralgic pains, anaesthesia of the skin and painless whitlows, with tissue loss, are features. In fact Zambaco has advanced the idea that Morvan’s disease is leprosy.
In syringomyelia the dissociation of sensation is marked, as with leprosy. In syringomyelia, however, the upper extremities are, as a rule, alone affected and the muscular atrophy is more of the scapulohumeral type, with involvement of trunk muscles causing scoliosis, than of the thenar and hypothenar eminences, so that while the fingers may be more contracted and rigid than in leprosy we do not get the main-en-griffe. The anaesthetic areas of syringomyelia continue to sweat, and we may also get spastic symptoms and speech defects in syringomyelia.
Raynaud’s disease has also been confused with leprosy.
Of the skin diseases the most important confusing lesions are the cutaneous manifestations of tuberculosis and syphilis. In lupus the tubercles are very much smaller, show the apple jelly appearance, the lesion spreads peripherally, is rather purplish and is not anaesthetic. Syphilitic ulcerations are more punched out, do not affect the same sites and respond to syphilitic treatment immediately. You do not find nerve enlargements in syphilis.
There is great lack of agreement as to the frequency of the Wassermann reaction in leprosy, some reporting a positive test as common in nodular leprosy while others have reported negative findings where there was not ground for suspecting syphilis. Nerve leprosy does not often give a positive test.
Fletcher obtained 22% positives in 100 cases of leprosy—28% in nodular and 17% in nerve cases. One-third of the cases gave a history of syphilis.
Sutherland and Mitra obtained 17 positive Wassermann reactions in 34 nodular cases, 16 positives in 52 anaesthetic cases and 8 positives in 14 cases of mixed leprosy. The sera of 12 children of leprous parents were negative.