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: In two patients ( DTD and AO2 / DTD ) , no other structural mutation was found , but polymerase chain reaction amplification and single - strand conformation polymorphism analysis of fibroblast cDNA showed reduced mRNA levels of the wild - type DTDST allele these two patients may be compound heterozygotes for the " Finnish " mutation ( as yet uncharacterized at the DNA level ) , which causes reduced expression of DTDST .
### Output Text:
In two patients ( <span class="disease">DTD</span> and <span class="disease">AO2</span> / <span class="disease">DTD</span> ) , no other structural mutation was found , but polymerase chain reaction amplification and single - strand conformation polymorphism analysis of fibroblast cDNA showed reduced mRNA levels of the wild - type DTDST allele these two patients may be compound heterozygotes for the " Finnish " mutation ( as yet uncharacterized at the DNA level ) , which causes reduced expression of DTDST . 