Table 3.

Demographics, clinical, and genetic characteristics of Hong Kong Mitochondrial Disease cases (total 119)

Characteristics	Number of patients (% of total)
Sex
Male	65 (54.6)
Female	54 (45.4)
Ethnicity
Chinese	112 (94.1)
Others	7 (5.9)
Age at onset
At birth to < 1 month	14 (11.8)
1 month to < 2 years	35 (29.4)
2 years to < 5 years	9 (7.6)
5 years to < 12 years	21 (17.6)
12 years to < 18 years	12 (10.1)
18 years or older	28 (23.5)
Clinical syndrome
Syndromic	74 (62.2)
Non-syndromic	45 (37.8)
Family history
Positive	51 (42.9)
Patients with mtDNA pathogenic variants	35 (68.6% of 51 cases)
Patients with nDNA pathogenic variants	15 (29.4% of 51 cases)
Unknown molecular basis	1 (2.0% of 51 cases)
Negative	68 (57.1)
Organ system involvement at presentation
Neurological	92 (77.3)
Hearing	14 (11.8)
Gastrointestinal	9 (7.6)
Endocrine	9 (7.6)
Cardiac	6 (5.0)
Renal	4 (3.4)
Ophthalmological	3 (2.5)
Hematological	1 (0.8)
Molecular genetic information
mtDNA pathogenic variants	72 (60.5)
nDNA pathogenic variants	38 (31.9)
Unknown molecular basis	9 (7.6)

mtDNA mitochondrial DNA, nDNA nuclear DNA