As we have begun to see more and more cases of COVID-19, the majority of the more severe cases have been found to be in the elderly population or people with underlying chronic conditions affecting the ability of the immune system to fight illness. We have yet to see many cases of confirmed COVID-19 in infants and children. However, recently there have been reports of children and adolescents with a multisystem inflammatory condition with symptoms similar to those seen in Kawasaki disease and toxic shock syndrome and required admission to intensive care units. It is thought that this multisystem inflammatory syndrome may be related to COVID-19. 
Kawasaki disease is an acute febrile illness usually occurring in children younger than 5 years of age. The fever usually lasts at least 5 days and is associated with rash, swelling of the hands and feet, swollen lymph glands in the neck and irritation and inflammation of the mouth and throat.
Toxic Shock Syndrome
Toxic shock syndrome is another condition that typically presents with a high fever. Associated symptoms include hypotension, diffuse erythematous rash, and organ dysfunction in at least two organ systems that may progress rapidly to severe shock. Toxic shock syndrome is typically caused by staphylococcal or streptococcal bacteria.
On May 14, 2020, the Centers for Disease Control and Prevention (CDC) released an official health advisory which provided background information on several cases of multisystem inflammatory syndrome in children (MIS-C) associated with coronavirus disease 2019 (COVID-19) along with a case definition of the syndrome. Cases have been reported in U.S. and other countries. 
Case Definition for Multisystem Inflammatory Syndrome in Children (MIS-C):
The CDC is recommending that healthcare providers who have treated or are currently treating patients meeting the criteria for (MIS-C) should report suspected cases to their local, state, or territorial health department.
As of April 1, 2020, there is no official coding guidance for MIS-C. MIS-C cannot be indexed in the ICD-10-CM Alphabetic Index therefore coders must follow the guidance in ICD-10-CM Official Guidelines for Coding and Reporting, Section I.B.15: Syndromes. This instructs the coder to assign codes for the documented manifestations of the syndrome. Any additional symptoms that are not an integral part of the disease process may be reported when the condition does not have a unique code.
NOTE: Changes to the official coding guidelines and rules beyond April 1, 2020 will render the Coding Guidance educational content invalid for future educational purposes.
Sandy Hall, Coding Education Auditor; CCS, COC, CPC