Table 1 Clinical summary of patients with hKIF21B variants.
Patient 1 | Patient 2 | Patient 3 | Patient 4 | |
|---|---|---|---|---|
Age at last evaluation | 10 y | 12 y 1 m | 9 y | 3 y 8 m |
Sex | Male | Male | Female | Male |
Genetics | ||||
Gene | KIF21B | KIF21B | KIF21B | KIF21B |
NM_001252100.1 | c.2032A>C | c.937C>A | c.3001G>A | c.2959_2962dupGCCA |
HGVS protein nomenclature | p.Ile678Leu | p.Gln313Lys | p.Ala1001Thr | p.Asn988Serfs*4 |
Inheritance | De novo | De novo | Inherited from the affected father | De novo |
Pregnancy and delivery | ||||
Pregnancy | Normal | Oligohydramnios and IUGR | Normal | Small for gestational age |
Height (perc)/weight(perc)/head circumference(perc) at birth | 51 cm (97th p), 3.750 kg (97th p), 33 cm (15th p) | 49 cm (49th p), 2.584 kg (7th p), 32 cm (5th p) | 3.480 kg (50th p) | 46.4 cm (7th p), 2.633 kg (5.87th p), *34 cm (25th p) *Measurements done at age 6 days |
Neonatal findings | None | Nuchal cord at birth and was blue, mild respiratory distress, but discharged with mother | None | Feeding issues, NG tube |
Developmental stages | ||||
Age of sitting (months) | 10 | Does not | 14 | 9 |
Age of walking (months) | 18 | Does not | 24 | 15–16 |
Language delay | Yes | Yes | Yes | No |
Age of first words (m:months, y:years) | 36 m | 36 m | 12 m | |
Age of first sentences (m:months, y:years) | NA | N/A | 24 m | |
Current language ability | Short sentences, dysarthria | Non-verbal | Sentences | Short sentences |
Intellectual disability (ID) | ||||
Estimated level of ID (mild, moderate, severe) | Borderline | Severe | Mild to moderate | Mild |
Age at evaluation (y) | 10 y | 9 y | ||
Total IQ | 66–79 (WISC V) | 54–59 (WISC V) | ||
Clinical examination | ||||
Age at examination (years) | 5 y | 12 y 1 m | 3 y 9 m | 3 y 8 m |
Height (SD)/weight(SD)/head circumference(SD) | 118 cm (+1.5), 21.3 kg (+2), 52 cm (+0.5) | 139 cm (−1.3), 20 kg (−3.4), 48.5 cm (−3.9) | 99 cm (−1.1), 17.8 kg (+1.8), 49.6 cm (−0.2) | 90.7 cm (−1.67), 16.3 kg (+0.09), 50.7 cm (+0.72) |
Neurologic examination | Slow | Poor visual fixation, constant tongue thrusting, poor gag, poor head control, bilateral ankle tightness, right wrist contracture | Mildly hypertonic legs | Hypotonia |
Dysmorphic features | Plagiocephaly | Large eyes, fleshy ears, hypertelorism | Epicanthic folds, mild ptosis, tented upperlip | Upslanting palpebral fissures, prominent eyebrows, broad nose with bulbous tip, anteverted nares. Micrognathia. Right-sided Duane syndrome |
Brain imaging (MRI) | ||||
Age at examination (m:months, y:years) | 3 y | 6 m and 12 y | 2 y | 1 y 9 m |
Brain anomalies (MRI) | Complete agenesis of the corpus callosum | Normal | No structural abnormalites, myelinisation not completed yet. Normal differentiation white and gray matter. No focal lesions. Normal spectroscopy | A few scattered punctate foci of T2 prolongation in subcortical white matter and periventricular white matter of bilateral cerebral hemispheres with no associated restricted diffusion or hemorrhage |
Other | ||||
History of falling spells with normal EEG. Severe constipation, Central sleep apnea, History of feeding issues requiring G tube | ||||
