Table 1.

ACC classification according to Frieden: [4]

Type	Short characteristic
I	ACC of the scalp without multiple anomalies. Autosomally dominant or sporadic
II	ACC of the scalp with limb reduction anomalies. Autosomally dominant.
III	ACC of the scalp associated with epidermal nevi or organ anomalies, associated with corneal opacity and delayed psychomotor development. Sporadic
IV	ACC with underlying embryological malformations such as myelomeningocele, spinal cord dystrophy and hemangiomas in the subarachnoid space. ACC in any location, usually the scalp or the abdomen.
V	ACC associated with fetus papyraceus and placental infarction. Defect in any location, usually symmetrical and linear. Occasionally accompanied by developmental retardation, nail dystrophy or dystrophy of finger and toe phalanges.
VI	ACC associated with epidermolysis bullosa (EB), usually on the limbs. Bullae on the skin and mucosa with accompanying abnormalities of the nails. Inheritance depends on the EB type.
VII	ACC located on the limbs, with no bullae and no malformations. Usually located in the shin area and on dorsal surfaces of the hands and feet. Autosomally dominant or recessive
VIII	ACC caused by teratogens such as a virus infection (rubella, herpes simplex) or exposure to methimazole. This type usually occurs on the scalp
IX	ACC associated with malformations, e.g. chromosome 13 trisomy or epidermal dysplasia.