Table 2 Classification of exceptionally rare diseases included in the present study according to Orphanet
From: Drug development for exceptionally rare metabolic diseases: challenging but not impossible
General classification | Total (N = 166) | Disease group classification | Total |
|---|---|---|---|
Metabolic disease involving complex molecules | 62 | Lysosomal diseases | 31 (50%) |
Purine or pyrimidine metabolism disorder | 10 (16%) | ||
Sterol metabolism disorder | 8 (13%) | ||
Metabolic neurotransmission anomaly | 5 (8%) | ||
Peroxisomal disease | 4 (6%) | ||
Metal transport or utilisation disorder | 3 (5%) | ||
Protein glycosylation disorder | 1 (2%) | ||
Metabolic intoxication disease | 36 | Amino or protein metabolism disorder | 34 (94%) |
Hyperoxaluria | 1 (3%) | ||
Methylmalonic aciduria - microcephaly - cataract | 1 (3%) | ||
Energy metabolism disorder | 45 | Mitochondrial disorder | 26 (58%) |
Fatty acid oxidation or ketogenesis disorder | 7 (9%) | ||
Creatine biosynthesis disorder | 2 (4%) | ||
Ketolysis disorder | 2 (4%) | ||
Enolase deficiency | 1 (2%) | ||
Gluconeogenesis disorder | 1 (2%) | ||
Hemolytic anemia due to glucophosphate isomerase deficiency | 1 (2%) | ||
Phosphoglycerate kinase 1 deficiency | 1 (2%) | ||
Pyruvate metabolism disorder | 1 (2%) | ||
Thiamine-responsive megaloblastic anemia syndrome | 1 (2%) | ||
Tricarboxylic acid cycle disorder | 1 (2%) | ||
Triose phosphate-isomerase deficiency | 1 (2%) | ||
Carbohydrate metabolism disorder | 12 | Glycogen storage disease | 7 (58%) |
Glucose transport disorder | 4 (33%) | ||
Familial hyperinsulinism | 1 (8%) | ||
Other metabolic disease | 11 | Metabolic disease associated with a progressive neurological disorder | 6 (55%) |
Miscellanous metabolic disease with mostly hepatic presentation | 4 (36%) | ||
Hereditary hypercarotenemia and vitamin A deficiency | 1 (9%) |