It was in most cases, vitiligo:
"—Biblical Data:

According to the Levitical text, the characteristic features of leprosy were: (1) bright white spots or patches on the skin the hair on which also was white; (2) the depression of the patches below the level of the surrounding skin; (3) the existence of "quick raw flesh"; (4) the spreading of the scab or scall.
Comparison with Modern Leprosy.

There are two forms of modern leprosy—the tubercular, or nodular, and the anesthetic, or nervous; generally both forms are present. The nodular form begins, as a rule, as round or irregularly shaped spots, commonly of a mahogany or sepia color. These often disappear, and are followed by the appearance of nodules. In an advanced stage the face is covered with firm, livid, nodular elevations: the nose, lips, and ears are swollen beyond their natural size, the eyelashes and eyebrows are lost, and the eyes are staring; the whole producing a hideous disfigurement. As the disease progresses, insensibility of the skin and paralysis ensue, and the fingers and toes may rot away.

In the Biblical description, one is immediately impressed by the absence of all allusion to the hideous facial deformity, the loss of feeling, and the rotting of the members. If such conspicuous manifestations had existed they could not possibly have escaped observation. The Levitical code prescribed that the several examinations of the person suspected should be made at intervals of seven days, thus enabling the priest to note the progress of the disease. Leprosy is an exceedingly slow disease, particularly in the beginning, and a fortnight would show absolutely no change in the vast majority of cases. Moreover, the "lepra Hebræorum" was a curable disease. When the leper was cured the priest made an atonement before the Lord, and expiatory sacrifices in the form of a sin-offering and a trespass-offering were made also. Modern leprosy is, except in isolated instances, incurable.
Nature of "Ẓara'at."

The probabilities are that "ẓara'at" comprised a number of diseases of the skin, which, owing to the undeveloped state of medical science at that period, were not distinguished. The white spots, upon which so much diagnostic stress was laid, were in all likelihood those of vitiligo, a disease quite common in tropical countries, and characterized by bright white spots, the hairs on which also become white. Vitiligo begins as small patches, which slowly spread, often involving ultimately large areas of the body's surface. The disease is harmless, but most disfiguring in those of swarthy complexion.

In the Septuagint "ẓara'at" is translated by "lepra." It is reasonable to assume that the Hebrews attached the same meaning to "ẓara'at" that the Greeks did to "lepra," which is derived from "lepros" (= "rough" or "scaly"). According to the medical writings of Ægineta, Ætius, Actuarius, Oribasus, and others, lepra was uniformly regarded as a circular, superficial, scaly eruption of the skin; in other words, their lepra was the psoriasis of modern times. There is absolutely nothing in the Greek description of lepra that suggests even in a remote manner the modern leprosy. The Greeks, in speaking of true leprosy, did not use the term "lepra," but "elephantiasis." It is evident, therefore, that they meant by "lepra" an affection distinct and apart from the disease of leprosy as now known. The confusion and obscurity that have enveloped this subject for centuries have resulted from the use of different terms in successive ages to designate the same disease, and from the total change in the meaning and application of the word "lepra."
Segregation.

There is much reason to believe that the segregation of lepers was regarded, at any rate at certain periods, more in the light of a religious ceremonial than as a hygienic restriction. Ẓara'at was looked upon as a disease inflicted by God upon those who transgressed His laws, a divine visitation for evil thoughts and evil deeds. Every leper mentioned in the Old Testament was afflicted because of some transgression. "Miriam uttered disrespectful words against God's chosen servant Moses, and, therefore, was she smitten with leprosy. Joab, with his family and descendants, was cursed by David for having treacherously murdered his great rival Abner. Gehazi provoked the anger of Elisha by his mean covetousness, calculated to bring the name of Israel into disrepute among the heathen. King . . . Uzziah was smitten with incurable leprosy for his alleged usurpation of priestly privileges in burning incense on the golden altar of the Temple" (Kalisch). It would have been quite natural for the people by a posteriori reasoning to have regarded persons afflicted with ẓara'at as transgressors; they had violated the laws of God and their transgressions had been great, else they would not have been so afflicted.

Writers who hold the view that the exclusion of lepers had chiefly a religious significance conclude from these facts that lepers were obliged to remain outside the camp because they were regarded as likely to morally infect others. As long as the signs of the disease remained upon them they were obliged to live outside the camp. It is reasonable to believe that, although Biblical and modern leprosy are, in all probability, not the same disease, thepresent custom of segregating lepers had its origin and stimulus in the Biblical example of segregating those afflicted with ẓara'at. Had the Bible never been written it is probable that lepers would to-day be permitted to go in and out among their fellows unhindered, for leprosy is a much less actively communicable disease than several other well-known affections in the case of which segregation is not practicable.

The Biblical description of leprosy of garments and houses is strikingly analogous in its wording to that of leprosy of persons. The passages in Leviticus (xiii. 47-59) are at present inexplicable in the light of modern science. The probabilities are that the description refers to stains upon garments produced by pus and blood from boils and ulcers of various kinds. Thus alone could the greenish and reddish stains be accounted for. That the description in Lev. xiv. 33-48 could not have applied to a leprosy of walls of houses is beyond reasonable doubt: such conceptions may possibly be ascribed to Oriental fancy and love of metaphor. Chemical incrustations and mildew were doubtless in this manner endowed with the symptoms of a living and spreading disease."
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