Constitutional mismatch repair deficiency (CMMRD) syndrome is a uncommon dysfunction that tremendously increases the chance of establishing one or additional varieties of most cancers in young children and younger older people. The cancers that most usually happen in CMMRD syndrome are cancers of the (big intestine) and rectum (collectively referred to as colorectal most cancers), brain, and blood (leukemia or lymphoma).

Almost all persons with CMMRD syndrome build most cancers ahead of age 18, typically in late childhood. The age of analysis varies relying on the most cancers variety brain cancers, leukemia, and lymphomas have a tendency to happen at more youthful ages than colorectal most cancers in persons with CMMRD syndrome. It is estimated that twenty to 40 per cent of persons with CMMRD syndrome who build most cancers will build another most cancers afterwards in lifestyle.

Folks with CMMRD syndrome may perhaps build a number of noncancerous (benign) growths (adenomas) in the colon that are likely to grow to be cancerous (malignant) more than time. Brain cancers in CMMRD syndrome generally contain sure cells known as glial cells, producing gliomas or glioblastomas. The most popular blood most cancers in CMMRD syndrome is known as which affects white blood cells. Other cancers that can happen in CMMRD syndrome involve cancers of , , or uterine lining ().

Lots of persons with CMMRD syndrome build features similar to individuals that happen in a situation known as neurofibromatosis variety one. These features involve adjustments in pores and skin coloring (pigmentation), which are characterised by one or additional flat patches on the pores and skin that are darker than the bordering region (). Some afflicted people have freckling or patches of pores and skin that are unusually light in colour (hypopigmented). Hardly ever, persons with CMMRD syndrome will build a attribute of neurofibromatosis variety one known as Lisch nodules, which are benign growths that generally look in the coloured element of the eye (the iris). Lisch nodules do not interfere with eyesight. Some persons with CMMRD syndrome are to begin with misdiagnosed with neurofibromatosis variety one.