We describe three previously healthy children, admitted from our emergency department (ED) to our free-standing children's hospital, as the first documented cases of croup as a manifestation of SARS-CoV-2 infection. All three cases (ages 11 months, 2 years, and 9 years old) presented with non-specific upper-respiratory-tract symptoms that developed into a barky cough with associated stridor at rest and respiratory distress. All were diagnosed with SARS-CoV-2 by polymerase chain reaction testing from nasopharyngeal samples that were negative for all other pathogens including the most common etiologies for croup. Each received multiple (≥3) doses of nebulized racemic epinephrine with minimal to no improvement shortly after medication. All had a prolonged period of time from ED presentation until the resolution of their stridor at rest (13, 19, and 21 h). All received dexamethasone early in their ED treatment and all were admitted. All three received at least one additional dose of dexamethasone, an atypical treatment occurrence in our hospital, due to each patient's prolonged duration of symptoms. One child required heliox therapy and admission to intensive care. All patients were eventually discharged. Pathogen testing is usually not indicated in croup, but with “COVID-19 croup,” SARS-CoV-2 testing should be considered given the prognostic significance and prolonged quarantine implications. Our limited experience with this newly described COVID-19 croup condition suggests that cases can present with significant pathology and might not improve as rapidly as those with typical croup.

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During perinatal development, avian and mammalian skeletal muscles express a novel set of troponin T (TnT) isoforms with higher M(r)s and more acidic pIs than their adult counterparts. In mammals, these TnTs result from the incorporation of a developmentally regulated 5'-fetal exon into fast TnT mRNAs. To determine whether chicken perinatal TnTs are generated by a similar mechanism, we sequenced 40 chicken TnT 5'-cDNAs from perinatal and adult pectoralis. Evidence for five 5'-exons not present in the mammalian gene was found, including one, y, whose splicing is developmentally regulated. Although none of these new exons are homologous with the mammalian fetal exon, their alternative splicing, superimposed on three conserved splicing patterns of the phylogenetically shared 5'-exons, generates the chicken perinatal TnT isoforms. These observations indicate that chicken, and most likely other avian species, evolved an independent 5'-alternative splicing mechanism to generate perinatal TnTs that have the same biophysical, and presumably functional, properties as their mammalian homologs.