In the sentence extracted from biomedical literature, identify all the disease entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="disease"> to denote a disease.

### Input Text: To study the molecular genetics of classical and Duarte galactosemia , we analyzed the GALT mutations in 30 families with classical galactosemia , in 10 families with the D - 2 variant and in 3 individuals carrying the D - 1 allele by denaturing gradient gel electrophoresis ( DGGE ) .
### Output Text:
To study the molecular genetics of <span class="disease">classical and Duarte galactosemia</span> , we analyzed the GALT mutations in 30 families with <span class="disease">classical galactosemia</span> , in 10 families with the D - 2 variant and in 3 individuals carrying the D - 1 allele by denaturing gradient gel electrophoresis ( DGGE ) . 