Multisystem disorders are often rare conditions. There may be limited information about such disorders, so they should be carefully modeled.

When determining parent concepts:

• A multisystem parent concept should be included.
• Genetic or inherited disorders should be modeled in the same way as other genetic and inherited disorders.
• The manifestations of the disorder must always necessarily be true before assigning the relevant parents.
• Attributes must also always necessarily be true.
  • For example,
    • 702410002 |Iris coloboma with ptosis, hypertelorism, and mental retardation (disorder)|  Since the coloboma of the iris is not always present, coloboma would not be explicitly modeled in the relationships. 

Some multisystem disorders can be named by their manifestations. The FSN should be descriptive rather than just a list of names.

For example,

• 717909004 |Bilateral microtia with deafness and cleft palate syndrome (disorder)|

A multisystem disorder with an eponymous syndrome name should be included as a synonym only.