Leprosy was a serious disease which caused the one who had it to be sent out from among the people to live isolated, away from anyone else. This was not the case for having an issue of blood.
Furthermore, priests were not called upon in the Levitical system to examine women who had an issue of blood. Had such been the case, every woman in Israel might have had to appear before the priest monthly, overwhelming the priesthood with such unnecessary duties.
Leprosy, once diagnosed by the priests, could only be pronounced clean by the priests (in the rare case that it had been cured).
Getting a Diagnosis of Leprosy
When a man shall have in the skin of his flesh a rising, a scab, or
bright spot, and it be in the skin of his flesh like the plague of
leprosy; then he shall be brought unto Aaron the priest, or unto one
of his sons the priests: And the priest shall look on the plague in
the skin of the flesh: and when the hair in the plague is turned
white, and the plague in sight be deeper than the skin of his flesh,
it is a plague of leprosy: and the priest shall look on him, and
pronounce him unclean. (Leviticus 13:2-3, KJV)
Being Pronounced Healed of Leprosy
And the priest shall go forth out of the camp; and the priest shall
look, and, behold, if the plague of leprosy be healed in the leper; .
. . . And he shall sprinkle upon him that is to be cleansed from the
leprosy seven times, and shall pronounce him clean, and shall let the
living bird loose into the open field. (Leviticus 14:3,7, KJV)
Both the diagnosis and the pronouncement of healing legally involved the priesthood. Jesus, who followed the law, instructed those whom he had healed to obey this law, not only for the sake of the law itself, but also for a witness against the priests--who knew very well that it was unusual to be healed of leprosy. This would give them evidence of Christ's Messiahship.
But if the lepers imprudently noised it about that they had been healed by Jesus, and the news had reached the priests' ears before they arrived to be pronounced clean, the prejudiced priests would have been prepared to resist, and might not have offered the correct diagnosis in their attempt to undermine Christ's influence. This is why Jesus gave such strict orders that they tell no one, but go directly to the priest with the offering that the law required.
The Law for an Issue of Blood
And if a woman have an issue, and her issue in her flesh be blood, she
shall be put apart seven days: and whosoever toucheth her shall be
unclean until the even. . . . And if a woman have an issue of her
blood many days out of the time of her separation, or if it run beyond
the time of her separation; all the days of the issue of her
uncleanness shall be as the days of her separation: she shall be
unclean. (Leviticus 15:19,25, KJV)
While a woman was "unclean" during her issue of blood, she was not required by this to visit the priest. The only time when a woman would bring an offering to the temple following an issue of blood was after the birth of a child: at 40 days after a son, and 80 days after a daughter.
Following a Birth
Speak unto the children of Israel, saying, If a woman have conceived
seed, and born a man child: then she shall be unclean seven days;
according to the days of the separation for her infirmity shall she be
unclean. (Leviticus 12:2, KJV)
And in the eighth day the flesh of his foreskin shall be circumcised.
(Leviticus 12:3, KJV)
And she shall then continue in the blood of her purifying three and
thirty days; she shall touch no hallowed thing, nor come into the
sanctuary, until the days of her purifying be fulfilled. (Leviticus
But if she bear a maid child, then she shall be unclean two weeks, as
in her separation: and she shall continue in the blood of her
purifying threescore and six days. (Leviticus 12:5, KJV)
And when the days of her purifying are fulfilled, for a son, or for a
daughter, she shall bring a lamb of the first year for a burnt
offering, and a young pigeon, or a turtledove, for a sin offering,
unto the door of the tabernacle of the congregation, unto the priest:
(Leviticus 12:6, KJV)
Who shall offer it before the LORD, and make an atonement for her; and
she shall be cleansed from the issue of her blood. This is the law for
her that hath born a male or a female. (Leviticus 12:7, KJV)
As can be seen, the law for leprosy was more particular than the general laws of uncleanness, such as a woman's issue of blood. Leprosy required the intervention of the priests, whereas other uncleannesses generally did not.