๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
EPIDEMIOLOGY
The porphyrias are rare disorders, occurring in all races and both sexes. Whereas some forms appear during infancy, other variants usually do not present until puberty or adulthood. Prevalence rates vary from 0.1 to 10 per 100โ000 individuals (see Table 49.2). However, the precise prevalence of the various porphyrias is not known, due primarily to geographic differences, the likelihood of underdiagnosis, and the incomplete penetrance of the dominantly inherited porphyrias.
Fig. 49.1 The heme biosynthetic pathway. ALA, aminolevulinic acid, also referred to as ฮด-aminolevulinic acid or 5-aminolevulinic acid.
Table 49.2 Classification of the porphyrias into acute and non-acute forms. Important clinical and epidemiological aspects are highlighted. ALA-D, aminolevulinic acid dehydratase; AR, autosomal recessive; MDS, myelodysplastic syndrome; MPD, myeloproliferative disorder.