Table 2.

Summary of dyskeratosis congenita diagnostic criteria.

Diagnosis	Criteria^15,16,43
DC^a	1. All three mucocutaneous features: • Abnormal skin pigmentation • Nail dystrophy • Leukoplakia 2. At least 1 out of 3 mucocutaneous feature, combined with bone marrow failure and 2 other somatic features of DC 3. Aplastic anaemia, myelodysplastic syndrome or pulmonary fibrosis associated with a pathogenic telomerase variant 4. 2 or more features seen in DC associated with very short telomeres that are below 1st centile.
Hoyeraal–Hreidarsson Syndrome	Four or more features of: 1. Growth retardation 2. Developmental delay 3. Microcephaly 4. Bone marrow failure 5. Immunodeficiency 6. Cerebellar hypoplasia

Diagnosis

Criteria^15,16,43

DC^a

1. All three mucocutaneous features:

• Abnormal skin pigmentation

• Nail dystrophy

• Leukoplakia

2. At least 1 out of 3 mucocutaneous feature, combined with bone marrow failure and 2 other somatic features of DC

3. Aplastic anaemia, myelodysplastic syndrome or pulmonary fibrosis associated with a pathogenic telomerase variant

4. 2 or more features seen in DC associated with very short telomeres that are below 1st centile.

Hoyeraal–Hreidarsson Syndrome

Four or more features of:

1. Growth retardation

2. Developmental delay

3. Microcephaly

4. Bone marrow failure

5. Immunodeficiency

6. Cerebellar hypoplasia

^aDyskeratosis congenita. References are in numerical superscript.