Segmental spinal muscular atrophy and dermatological findings in a patient with chromosome 18q deletion

Abnormalities of Skin and Cutaneous Appendages in Neuromuscular Disorders

OBJECTIVES

A thorough evaluation of the skin and its appendages is frequently outside the area of expertise of the neurologist who deals with neuromuscular disorders. However, the skin is more frequently affected in neuromuscular disorders and deserves more attention than so far acknowledged.

METHODS

Review of publications by searching Medline dealing with skin disorders in neuromuscular disorders.

RESULTS

Skin abnormalities are most frequently found in patients with dermatomyositis, myotonic dystrophies, mitochondrial disorders, muscular dystrophies, and neuropathies. The hairs and the sweat glands are the appendages most frequently affected in neuromuscular disorders. In myotonic dystrophies and mitochondrial disorders there are indications that the rate of skin neoplasms is increased compared with the general population.

CONCLUSIONS

Skin lesions in neuromuscular disorders are not unusual. Neurologists should be aware of the cutaneous implications of neuromuscular disorders and should take a thorough history relative to cutaneous manifestations and complete a comprehensive investigation of the skin and its appendages. If there is evidence of a dermatological problem in a neuromuscular disorder, a dermatologist should be consulted. Dermatological involvement in neuromuscular disorders may contribute to the diagnosis of neuromuscular disorders and may help to differentiate between various entities. The skin should become a focus of the neurologist as well.

Adults with Chromosome 18 Abnormalities

The identification of an underlying chromosome abnormality frequently marks the endpoint of a diagnostic odyssey. However, families are frequently left with more questions than answers as they consider their child's future. In the case of rare chromosome conditions, a lack of longitudinal data often makes it difficult to provide anticipatory guidance to these families. The objective of this study is to describe the lifespan, educational attainment, living situation, and behavioral phenotype of adults with chromosome 18 abnormalities. The Chromosome 18 Clinical Research Center has enrolled 483 individuals with one of the following conditions: 18q-, 18p-, Tetrasomy 18p, and Ring 18. As a part of the ongoing longitudinal study, we collect data on living arrangements, educational level attained, and employment status as well as data on executive functioning and behavioral skills on an annual basis. Within our cohort, 28 of the 483 participants have died, the majority of whom have deletions encompassing the TCF4 gene or who have unbalanced rearrangement involving other chromosomes. Data regarding the cause of and age at death are presented. We also report on the living situation, educational attainment, and behavioral phenotype of the 151 participants over the age of 18. In general, educational level is higher for people with all these conditions than implied by the early literature, including some that received post-high school education. In addition, some individuals are able to live independently, though at this point they represent a minority of patients. Data on executive function and behavioral phenotype are also presented. Taken together, these data provide insight into the long-term outcome for individuals with a chromosome 18 condition. This information is critical in counseling families on the range of potential outcomes for their child.

Autoimmune polyendocrinopathy associated with ring chromosome 18

Phenotypic and clinical features of individuals with ring chromosome 18 [r(18)] vary with the extent of deletion of the short (18p-) or long arm (18q-). Most patients with r(18), therefore, demonstrate a clinical spectrum of both 18p- and 18q- deletions. Short stature, microcephaly, mental and motor retardation, craniofacial dysmorphism and extremity abnormalities are the most commonly reported features in patients with r(18). Abnormalities of chromosome 18, especially 18p- syndrome, are often reported with autoimmune thyroid disease and growth hormone deficiency, but reports of endocrine abnormalities associated with r(18) are rare. Here, we report a case of an African-American female with hyperthyroidism, type 1 diabetes mellitus, vitiligo and IgA deficiency associated with a r(18) chromosome complement. This patient additionally had mild intellectual disability and dysmorphic features. Karyotype analysis showed a de novo ring chromosome 18 (deletion 18q23-18qter and deletion 18p11.3-18pter). Although this unique association of autoimmune polyglandular endocrinopathy with ring chromosome 18 could be coincidental, we speculate that a gene or genes on chromosome 18 might play a role in the autoimmune process.

18q deletions: Clinical, molecular, and brain MRI findings of 14 individuals

We studied 14 individuals with partial deletions of the long arm of chromosome 18, including terminal and interstitial de novo and inherited deletions. Study participants were examined clinically and by brain MRI. The size of the deletion was determined by segregation analysis using microsatellite markers. We observed that the phenotype was highly variable, even in two families with three 1st degree relatives. Among the 14 individuals, general intelligence varied from normal to severe mental retardation. The more common features of 18q-deletions (e.g., foot deformities, aural atresia, palatal abnormalities, dysmyelination, and nystagmus) were present in individuals lacking only the distal portion 18q22.3-qtel. Interstitial deletions exerted very heterogeneous effects on phenotype. In individuals with distal 18q22.3-q23 deletions, brain MRI was very distinctive with poor differentiation of gray and white matter on T2-weighted images.

Chromosome 18 aberrations and epilepsy: a review

Epilepsy is commonly observed in patients with chromosomal aberrations. We evaluated epilepsy and electroencephalographic (EEG) features in a group of patients carrying aberrations of chromosome 18. Fourteen patients were recruited: five with an 18p deletion syndrome (18pDS); six with an 18q deletion syndrome (18qDS); two with trisomy 18p syndrome; and one with a 45,XY,t(17-18) (cen-q11.2) karyotype. Patients with 18pDS had neither epilepsy nor EEG anomalies; four patients with 18qDS had epilepsy with partial seizures occurring during infancy or early childhood. Partial seizures were also present in both patients with trisomy 18p. By contrast, mixed seizures were observed in the patient carrying a translocation between chromosomes 17 and 18. Our data and a re-evaluation of the literature suggest that epilepsy is infrequent in patients with 18pDS. Conversely, partial seizures and focal EEG anomalies may be observed in those with patients with 18qDS. Our observations suggest that the haplo-insufficiency of genes located on the long arm of chromosome 18 is more likely to be associated with epilepsy, than is haplo-insufficiency of genes located on the short arm. While further EEG/clinical investigations are needed to validate these observations, this study indicates a possible relationship between chromosome 18 genes and epilepsy.

18q? Syndrome: Brain MRI shows poor differentiation of gray and white matter on T2-weighted images

PURPOSE

To study brain MRI findings in patients with 18q- syndrome and to correlate these findings with the results of the molecular breakpoint analysis.

MATERIALS AND METHODS

Brain MR images of 17 patients with 18q- syndrome were evaluated. Segregation analysis was performed with 15 microsatellite markers to determine the deletion breakpoints and whether the deletion included the myelin basic protein (MBP) gene.

RESULTS

One patient had an interstitial deletion of 18q which spared the MBP gene. He was the only one with normal brain MRI. All 16 patients with deletions including the MBP gene had abnormal white matter in MRI. The main finding was poor differentiation of gray and white matter on T2-weighted images due to increased white matter signal intensity. In addition, measured signal intensity of the white matter was significantly increased in patients compared with controls.

CONCLUSIONS

Poor differentiation of gray and white matter on T2-weighted images is the most typical MRI finding of the 18q- syndrome. These results support the postulation that abnormal myelination in 18q- syndrome is due to haploinsufficiency at or near the MBP locus.

Molecular characterization of a patient with central nervous system dysmyelination and cryptic unbalanced translocation between chromosomes 4q and 18q

We report on a 12-year-old boy who presented with delayed development and CNS dysmyelination. Genetic studies showed a normal 46,XY karyotype by routine cytogenetic analysis, and 46,XY.ish del(18)(q23)(D18Z1+, MBP-) by FISH using a locus-specific probe for the MBP gene (18q23). Though the patient appeared to have normal chromosome 18s by repeated high resolution banding analysis, his clinical features were suggestive of a deletion of 18q. These included hearing loss secondary to stenosis of the external auditory canals, abnormal facial features, and foot deformities. FISH studies with genomic probes from 18q22.3 to 18qter confirmed a cryptic deletion which encompassed the MBP gene. In an attempt to further characterize the deletion, whole genome screening was conducted using array based comparative genomic hybridization (array CGH) analysis. The array CGH data not only confirmed a cryptic deletion in the 18q22.3 to 18qter region of approximately 7 Mb, it also showed a previously undetected 3.7 Mb gain of 4q material. FISH studies demonstrated that the gained 4q material was translocated distal to the 18qter deletion breakpoint. The 18q deletion contains, in addition to MBP, other known genes including CYB5, ZNF236, GALR1, and NFATC1, while the gained 4q material includes the genes FACL1 and 2, KLKB1, F11 and MTNR1A. The use of these combined methodologies has resulted in the first reported case in which array CGH has been used to characterize a congenital chromosomal abnormality, highlighting the need for innovative molecular cytogenetic techniques in the diagnosis of patients with idiopathic neurological abnormalities.

Definition of a critical region on chromosome 18 for congenital aural atresia by arrayCGH

Deletions of the long arm of chromosome 18 occur in approximately 1 in 10,000 live births. Congenital aural atresia (CAA), or narrow external auditory canals, occurs in approximately 66% of all patients who have a terminal deletion 18q. The present report describes a series of 20 patients with CAA, of whom 18 had microscopically visible 18q deletions. The extent and nature of the chromosome-18 deletions were studied in detail by array-based comparative genomic hybridization (arrayCGH). High-resolution chromosome-18 profiles were obtained for all patients, and a critical region of 5 Mb that was deleted in all patients with CAA could be defined on 18q22.3-18q23. Therefore, this region can be considered as a candidate region for aural atresia. The array-based high-resolution copy-number screening enabled a refined cytogenetic diagnosis in 12 patients. Our approach appeared to be applicable to the detection of genetic mosaicisms and, in particular, to a detailed delineation of ring chromosomes. This study clearly demonstrates the power of the arrayCGH technology in high-resolution molecular karyotyping. Deletion and amplification mapping can now be performed at the submicroscopic level and will allow high-throughput definition of genomic regions harboring disease genes.

De novo deletion of chromosome 18q in a baby with harlequin ichthyosis

Harlequin ichthyosis, (MIM 242500), is a rare, autosomal recessive skin disorder due to an inborn error of epidermal keratinization. The gene for this condition has not been localized. We present a case of HI in which there was a de novo deletion of chromosome 18q: the karyotype was 46, XY, del(18)(q21.3). We postulate that the gene for HI may lie at, or distal to 18q21.3 and that the deletion observed in this case may have unmasked this autosomal recessive disorder.

Abnormal myelination in a patient with deletion 14q11.2q13.1

A male carrying an interstitial deletion of chromosome 14, presumably del(14)(q11.2q13), and presenting with abnormal myelination on magnetic resonance imaging is described. The abnormal myelination was evidenced as a high-signal intensity on T(2)-weighted magnetic resonance imaging. The patient had severe neurologic signs, various dysmorphic features, and a marked microcephaly. To our knowledge, this case is the first patient reported with abnormal myelination and a deletion of chromosome 14.

Chromosome 18q paracentric inversion in a family with mental retardation and hearing loss

We report on a mother and child with a paracentric inversion of the long arm of chromosome 18: 46,XX,inv(18)(q21.1q23). The child had findings in common with those seen in 18q- syndrome including: microcephaly, epicanthal folds, midface hypoplasia, and abnormally modeled ears, dermatoglyphic whorls on fingertips, clubfeet, hearing loss, and developmental delay. The mother and several maternal relatives had mild mental retardation and hearing loss. Magnetic resonance imaging of the child's brain showed abnormal myelination. Molecular studies including PCR-based markers for the MBP locus and fluorescent in situ hybridization with a P1 genomic clone on mother and child demonstrated only one copy of the MBP locus (18q23) with the deletion extending beyond the MBP locus. Therefore, the deletion in the MBP region may account for the abnormal myelination seen in the patient. The other clinical findings, including mental retardation and hearing loss in this family, may reflect disruption of distal or proximal genes within the deleted MBP region or at the more proximal breakpoint 18q21.1, and may represent a contiguous gene syndrome. Further study of this family may help define those genes functioning in the MBP region that contribute to the phenotype of 18q- syndrome.

Magnetic resonance imaging demonstrates incomplete myelination in 18q- syndrome: evidence for myelin basic protein haploinsufficiency

Magnetic resonance imaging (MRI) and MRI relaxometry were used to investigate disturbed brain myelination in 18q- syndrome, a disorder characterized by mental retardation, dysmorphic features, and growth failure. T1-weighted and dual spin-echo T2-weighted MR images were obtained, and T1 and T2 parametric image maps were created for 20 patients and 12 controls. MRI demonstrated abnormal brain white matter in all patients. White matter T1 and T2 relaxation times were significantly prolonged in patients compared to controls at all ages studied, suggesting incomplete myelination. Chromosome analysis using fluorescence in situ hybridization techniques showed that all patients with abnormal MRI scans and prolonged white matter T1 and T2 relaxation times were missing one copy of the myelin basic protein (MBP) gene. The one patient with normal-appearing white matter and normal white matter T1 and T2 relaxation times possessed two copies of the MBP gene. MRI and molecular genetic data suggest that incomplete cerebral myelination in 18q- is associated with haploinsufficiency of the gene for MBP.

Analysis of clinical variation seen in patients with 18q terminal deletions

Twenty-six patients with deletions of 18q were analyzed at the clinical and molecular levels in an attempt to delineate regions of chromosome 18 important to the 18q- syndrome phenotype. Molecular cytogenetic analysis was carried out using fluorescence in situ hybridization (FISH), and deletions ranging from 18q21.1-qter to 18q22.3-qter were detected. The parental origin of the deletions was determined by the analysis of inheritance of microsatellite markers. No correlation between size, parental origin, or severity of the resulting phenotype was found. The results suggest that a critical region for 18q- syndrome lies in the most distal portion of 18q and that it confers susceptibility for the various clinical manifestations of the 18q- syndrome when present in one copy.

Cytogenetic analysis of 23 Japanese patients with amyotrophic lateral sclerosis

The cytogenetic analysis of 23 Japanese patients with amyotrophic lateral sclerosis is reported. G-banded chromosomes of cultured peripheral blood lymphocytes of one subject had a constitutional chromosomal translocation, t(7;13)(p22;q21). No constitutional chromosome abnormality was found in any of the other 22 Japanese patients with amyotrophic lateral sclerosis tested.

Delayed myelination in a patient with 18q- syndrome

A Japanese boy with the typical manifestations of 18q-syndrome and delayed myelination on magnetic resonance imaging is described. Cytogenetic investigation revealed a deletion at 18q21.3. Three serial magnetic resonance images demonstrated that myelination in the central nervous system was delayed except for the corpus callosum and brainstem. This pattern of delayed myelination appears to be peculiar to the 18q- syndrome. Because the gene for myelin basic protein has been localized to the distal end of the long arm of chromosome 18, we speculate that the abnormal myelination in our patient was partly due to the failure of expression of the myelin basic protein gene.

Unbalanced translocation, t(18;21), detected by fluorescence in situ hybridization (FISH) in a child with 18q- syndrome and a ring chromosome 21

We report on an 8-year-old girl with minor anomalies consistent with 18q- syndrome and mild developmental delay. Initially cytogenetics showed a terminal deletion of chromosome 21 with mosaicism for a small ring chromosome 21 as the only apparent karyotypic abnormality: mos 45,XX,-21/46,XX,+r(21) (48%/52%). Further studies including FISH and DNA analysis demonstrated a de novo unbalanced translocation of chromosomes 18 and 21 with the likely breakpoints in 18q23 and 21q21.1. Most of 21q was translocated to the distal long arm of one chromosome 18, and this derivative 18 appeared to lack 18q23-qter. The small ring chromosome 21 [r(21)], present in only 52% of the patient's blood lymphocytes, did not appear to be associated with the abnormal phenotype since all 13 chromosome 21 markers that were examined in genomic DNA were present in 2 copies, and the phenotype of the patient was consistent with the 18q- syndrome. The karyotype was reinterpreted as mos 45,XX,-18,-21,+der(18) t(18;21) (q23;q21.1)/46,XX,-18,-21,+der(18) t(18;21) (q23;q21.1), +r(21) (p13q21.1) (48%/52%). These results demonstrate the power of FISH in conjunction with DNA analysis for examination of chromosome rearrangements that may be misclassified by traditional cytogenetic studies alone.

Congenital cervical spinal muscular atrophy: a non-familial, non progressive condition of the upper limbs

Two patients with congenital cervical spinal muscular atrophy had symmetrical severe muscle weakness and wasting confined to the upper limbs, areflexia and congenital contractures. The shoulders were internally rotated, elbows extended and wrists flexed. There were no sensory or bulbar symptoms, scoliosis, long tract signs or lower limb involvement. This condition should be regarded as a neurogenic type of arthrogryposis, limited to the upper limbs.

Progressive juvenile segmental spinal muscular atrophy

Juvenile segmental spinal muscular atrophy (JSSMA) typically involves the distal upper extremities and follows a benign course over 2-4 years then stabilizes. We report 2 males who presented in their teens with insidious distal upper extremity atrophy and weakness as in typical JSSMA but who then progressed to involvement of the lower extremities and hyperreflexia. There was no sensory loss. Electromyography and muscle biopsy demonstrated features consistent with localized anterior horn cell dysfunction. These patients are noteworthy because they demonstrate that some patients with JSSMA also may have involvement of the lower limbs several years after initial presentation. Progressive JSSMA may be categorized in the clinical spectrum between the spinal muscular atrophies and amyotrophic lateral sclerosis.