Table 1.
Clinical features of patients with a homozygous SMG9 gene variant c.551T > C p.(Val184Ala).
| Patient 1 | Patient 2 | Patient 3 | Patient 4 | Patient 5 | |
|---|---|---|---|---|---|
| Age | 25 y | 56 y | 54 y | 29 y | 26 y |
| Sex | Male | Male | Male | Male | Male |
| Birth length | 51 cm (−0.1 SD) | 52 cm (+0.5 SD) | NA | 50 cm (−0.6 SD) | 46 cm (−2.7 SD) |
| Birth weight | 3,590 g (−1%) | 3,550 g (−8%) | 3450 g | 3270 g (−4%) | 2535 g (−6%) |
| Birth OFC | 35.5 cm (+0.2 SD) | NA | NA | 35.5 cm (+0.2 SD) | 32 cm (−2.4 SD) |
| Current height | 183 cm (+0.4 SD) | 172 cm (−1.4 SD) | 181 cm (0.0 SD) | 171 cm (−1.6 SD) | 165 cm (−2.6 SD) |
| Current weight | 78 kg (+11%) | 73 kg (+22%) | 73.4 kg (+7%) | 85 kg (+44%) | 75 kg (+40%) |
| Current OFC | 59.7 cm (+1.8 SD) | 57 cm (−0.3 SD) | 59 cm (+1.0 SD) | 54.5 cm (−1.8 SD) | 55 cm (−1.7 SD) |
| Congenital heart defect | No | No | No | TGA, VSD, ASD, PDA, hypoplastic RA | No |
| Muscular hypotonia | No | No | No | Yes | Yes |
| Tendency to fall as a child | Yes | Yes | Yes | Yes | Yes |
| Independent walking age | 1 y and 3 m | 1 y and 8 m | 1 y and 3 m | 1 y and 6 m | 1 y and 7 m |
| First words age | 2 y | 2 y | 3.5 y | 2.5 y | 3 y |
| Language development | Markedly delayed | Markedly delayed | Markedly delayed | Markedly delayed | Markedly delayed |
| AAC methods | Signs, pictures, gestures used as a child | No | No | Gestures used as a child | Signs, pictures used as a child |
| Oral motor dyspraxia | Yes | Yes | Yes | Yes | Yes |
| Severity of ID | Mild | Borderline mild/moderate | Moderate | Moderate | Moderate |
| Word-finding difficulties | Yes | No | Mild | No | Mild |
| Epilepsy | No | No | No | No | No |
| EEG | N/A | Spike and slow-wave complexes | Bitemporal symmetric spike and slow-wave discharges | N/A | Slow background activity, spike and slow-wave complexes |
| Brain MRI | Mild dilatation of LV, mild lack of WM in the trigonum | N/A | N/A | Normal | Normal |
| Tendon reflexes | Clonic ankle reflexes, brisk patella reflexes | Clonic ankle reflexes, brisk patella reflexes | Clonic ankle reflexes, brisk patella reflexes | Clonic ankle reflexes, brisk patella and brachioradialis reflexes | Clonic ankle reflexes, brisk patella and brachioradialis reflexes |
| Intention tremor | + | + | ++ | ++ | + |
| Ataxia | No | Yes, as a child | Yes, as a child | Yes, as a child | Yes, as a child |
| Diadochokinesis | Slow | Slow | Slow | Slow | Slow |
| Increased muscle tone in lower limbs | + | ++ | ++ | ++ | + |
| Strabismus | Alternating esotropia, hypertropia (L), hypotropia (R), operated | No | Alternating exotropia, operated | Exotropia (R), hypertropia (R), no operation | Exotropia (R), hypertropia (R), operated |
| High palate | Yes | No | No | Yes | Yes |
| Planovalgus | Yes | No | No | Yes | Yes |
| Infections | Recurrent otitis media infections before school age | One otitis media infection before school age | One otitis media infection before school age | Recurrent otitis media infections before school age | Recurrent otitis media infections before school age |
| Dysmorphism | Depressed nasal bridge, broad nose | Low insertion of columella, long nose, depressed nasal bridge | Low insertion of columella, long nose, depressed nasal bridge | Brachycephaly, depressed nasal bridge | Prominent forehead, depressed and wide nasal bridge, broad nasal tip, low insertion of columella |
| Other | Mild scoliosis | High BP, hypercholesterolemia | High BP, type 2 DM, benign PH | Brachydactyly | Sacral dimple, brachydactyly |
Characteristic features were ID, pyramidal signs, and ocular manifestations. Abbreviations: y years, m months, - not present, + present, ++ markedly present, SD standard deviation from the mean, NA not available, OFC occipitofrontal circumference, TGA transposition of the great arteries, VSD ventricular septal defect, ASD atrial septal defect, PDA patent ductus arteriosus, RA right atrium, ID intellectual disability, LV lateral ventricles, WM white matter, BP blood pressure, DM diabetes mellitus, PH prostate hyperplasia, L left, R right.