Table 1.
Families with XLMR: Association with Skewed X Inactivation
|
No. of Carriersb |
||||||
| Familya | XLMR Disorder | Region ofLinkage | Total | With InactivationPattern ⩾80:20 | Xid | Descriptionc |
| Strong association (n=4): | ||||||
| K8135 | XLMR, short stature, tremor | q22-q24 | 5 | 5 | 1/1 | Short stature, tremor, behavioral abnormalities |
| K8210 | Williams | q28 | 4 | 4 | 3/3 | Muscle hypoplasia, hypotonia, frontal bossing, death at early age |
| K8300 | Pai | q28 | 7 | 7 | 3/3 | Profound mental retardation, death at early age, nonambulatory |
| K8435 | Mulvenna-Trotter-Fisher | q27 | 7 | 7 | 4/4 | Seizures, IgE deficiency, large head, moderate mental retardation |
| Incomplete association (n=14): | ||||||
| K8005 | Allan-Herndon Dudley | q13-q21 | 3 | 1 | Severe mental retardation, severe hypotonia, ataxia, abnormal facies | |
| K8090 | Allan-Herndon Dudley | q13-q21 | 2 | 0 | Severe mental retardation, severe hypotonia, ataxia, abnormal facies | |
| K8225 | Allan-Herndon Dudley | q13-q21 | 2 | 1 | Severe mental retardation, severe hypotonia, ataxia, abnormal facies | |
| K8020 | Aarskog-Scott | q11.21 | 3 | 0 | Short stature, facial, skeletal, and urogenital anomalies | |
| K8250 | Aarskog-Scott | q11.21 | 2 | 2 | 2/2 | Short stature, facial, skeletal, and urogenital anomalies |
| K8285 | Aarskog-Scott | q11.21 | 3 | 0 | Short stature, facial, skeletal, and urogenital anomalies | |
| K8765 | Agenesis corpus collosum | q28 | 7 | 2 | 1/1 | Neuromuscular spasticity, unsteady gait |
| K8065 | MRX7 | p11-p14 | 6 | 3 | 2/2 | Nonspecific XLMR |
| K8355 | XLMR, seizures, ataxia | p21-p11.2 | 6 | 2 | Seizures, ataxia, aphasia, autism | |
| K8070 | Miles-Carpenter MRSX4 | q13-q22 | 5 | 3 | 3/3 | Arched fingertips, microcephaly |
| K8240 | XLMR with cleft lip/palate | q12-q21 | 5 | 3 | 1/1 | Sloped forehead, short stature, small testicular volume |
| K8615 | XLMR, spastic paraplegia | p12-q12 | 3 | 2 | Spastic paraplegia, club feet, dystonia | |
| K8075 | Wieacker-Wolff | Proximal X q arm | 2 | 1 | Neuromuscular, muscle atrophy | |
| K8610 | FG syndrome | q13-q21 | 2 | 1 | Macrocephaly, imperforate anus, and congenital hypotonia | |
| No apparent association (n=6): | ||||||
| K8035 | XLMR, arched fingerprints | q13-q21 | 3 | 0 | Arched fingerprints, hypotonia, areflexia | |
| K8045 | Arena | q22-q25 | 2 | 0 | Severe spastic paraplegia, ataxia | |
| K8100 | Armfield | q28 | 3 | 0 | Short stature, cleft palate, seizures, glaucoma, severe mental retardation | |
| K8295 | Lujan | None | 4 | 0 | Marfanoid, triangular facies, narrow palate, hypernasal voice | |
| K8395 | XLMR, spastic paraplegia | Proximal X q arm | 2 | 0 | Spastic paraplegia, nystagmus; carriers have gait abnormalities | |
| K8450 | MRX32 | p21-p22.2 | 6 |
0 |
Nonspecific and variable mental retardation | |
| Total | 20 distinct disorders | 94 | 44 | 20/20 | ||
a
Most of the families have been described elsewhere (Lubs et al. 1996).
b
Carrier or noncarrier status was determined by linkage analysis, by pedigree analysis (in the case of obligate carriers) and, where possible, by direct mutation screening.
c
Specific clinical features are provided in the Miami XLMR database (Cabezas et al. 1999).
d
Xi = inactive X chromosome; data are number of informative carriers in whom the mutation was present on the preferentially inactive X chromosome/total number of informative carriers.