A Consensus Conference utilizing available literature and expert opinion sponsored by the American College of Medical Genetics in October 1995 evaluated the rational approach to the individual with mental retardation. Although no uniform protocol replaces individual clinician judgement, the consensus recommendations were as follows: 1. The individual with mental retardation, the family, and medical care providers benefit from a focused clinical and laboratory evaluation aimed at establishing causation and in providing counseling, prognosis, recurrence risks, and guidelines for management. 2. Essential elements of the evaluation include a three-generation pedigree: pre-, peri-, and post-natal history, complete physical examination focused on the presence of minor anomalies, neurologic examination, and assessment of the behavioral phenotype. 3. Selective laboratory testing should, in most patients, include a banded karyotype. Fragile X testing should be strongly considered in both males and females with unexplained mental retardation, especially in the presence of a positive family history, a consistent physical and behavioral phenotype and absence of major structural abnormalities. Metabolic testing should be initialed in the presence of suggestive clinical and physical findings. Neuroimaging should be considered in patients without a known diagnosis especially in the presence of neurologic symptoms, cranial contour abnormalities, microcephaly, or macrocephaly. In most situations MRI is the testing modality of choice. 4. Sequential evaluation of the patient, occasionally over several years, is often necessary for diagnosis, allowing for delineation of the physical and behavioral phenotype, a logical approach to ancillary testing and appropriate prognostic and reproductive counseling.

Evaluation of mental retardation: Recommendations of a consensus conference

Many cases of autism appear to be caused by several abnormal genes acting in concert The literature on chromosomal aberrations in autism is reviewed, with a view to finding potential gene markers for the neuropsychiatric disorder Most of the chromosomes have been implicated in the genesis of autism However, aberrations on the long arm of Chromosome 15 and numerical and structural abnormalities of the sex chromosomes have been most frequently reported These chromosomes appear to hold particular promise in the search for candidate genes

Chromosomal Disorders and Autism.

Editor—Holt-Oram syndrome (HOS) is a developmental disorder characterised by malformations of the radial ray of the forelimb and by congenital heart disease.1 The syndrome shows a marked variability in phenotype, with radial ray defects ranging from minor thumb abnormality through to severe reduction defect or phocomelia. The cardiac manifestations of HOS are similarly varied, and patients can present with a variety of structural heart abnormalities, atrial septal defects (ASDs) and ventricular septal defects (VSDs) being the most common, or conduction defects evident on ECG profiles. Previous studies have shown no correlation between the severity of a patient's cardiac and skeletal abnormalities.2 Intrafamilial variation can be wide.

HOS shows autosomal dominant inheritance and mutations in the T box transcription factor gene ( TBX5 ) have been shown previously to be responsible for this disorder.3 4There is also evidence for genetic heterogeneity.5 The mechanism by which mutations in TBX5 cause a dominant phenotype is not understood at present, and it is anticipated that knowledge of the type of mutations causing HOS may shed light on this. Knowledge of a large number of mutations and the relation of a person's genotype to phenotype is also useful for genetic counselling. In the face of a growing demand for a molecular diagnostic test for HOS, it is also helpful to have a quantitative estimate of the ability of current methods to detect mutations in TBX5 .

Twenty five cases with a clinical diagnosis of Holt-Oram syndrome have been tested for this study, bringing to 47 the total number of cases studied by us. Minimal diagnostic criteria were as described previously2: bilateral radial ray defect, plus either cardiac abnormality or family history of cardiac abnormality. Cases were referred by a variety of clinicians and underwent full clinical assessment including …

https://jmg.bmj.com/content/jmedgenet/37/10/785.full.pdf

The mutation spectrum in Holt-Oram syndrome

We report on 11 cases of isochromosome 12p mosaicism (or Pallister mosaic aneuploidy syndrome) in which the isochromosome is usually absent in cultured lymphocytes but present in fibroblasts. The patients range in age from a 22-week-gestation fetus to a 45-year-old man. They have a distinct pattern of anomalies which enables one to make a diagnosis based on clinical manifestations alone. Craniofacial manifestations include "coarse" face with prominent forehead, sparsity of scalp hair, hypertelorism, epicanthal folds, flat bridge of nose, and highly arched palate. Affected newborn infants are profoundly hypotonic with sparsity of scalp hair especially bitemporally and a prominent forehead. Most have accessory nipples. Birthweight and growth parameters are usually normal; however, some newborn infants are unusually large. In infancy, the facial appearance becomes "coarse," hypotonia persists, and seizures may occur. As adults, growth may be normal, scalp hair is thicker and the mandible becomes prominent. Most have a generalized pigmentary dysplasia which may be evident with a Wood's lamp only. All cases have been sporadic and there is no consistent pattern of advanced parental age.

Isochromosome 12p mosaicism (Pallister mosaic aneuploidy or pallister-killian syndrome): report of 11 cases

Biologic and clinical significance of cytogenetic and molecular cytogenetic abnormalities in benign and malignant cartilaginous lesions

In this report we summarize the findings in a genetic-diagnostic survey of an institutionalized population of 173 severely mentally retarded patients. The etiological study was based on a clinical genetic approach with special attention for dysmorphology and neurological findings. A constitutional disorder, as the direct cause of the severe mental handicap, was found in 75 patients (43.35%). A detailed survey of the different data and findings are given, and compared with the results of previous studies.

A genetic‐diagnostic survey in an institutionalized population of 173 severely mentally retarded patients

A 24-year-old female with severe mental retardation, congenital malformations and dysmorphic features is described. 8p trisomy due to a de novo inv dup(8) (p21.1----p22) was found in her karyotype. Other published cases with 8p trisomy are reviewed.

Partial 8p trisomy due to interstitial duplication: karyotype: 46, XX, inv dup(8) (p21.1→p22)

In the present paper an intercalary deletion of band 8q23 is reported in another patient with Langer-Giedion syndrome. These data confirm that the deletion in 8q responsible for this malformation syndrome is located at band 8q23.

Langer-Giedion syndrome and deletion of the long arm of chromosome 8. Confirmation of the critical segment to 8q23.

A 5-year-old boy with severe mental handicap, dysmorphic stigmata and a tetrasomy 21 in fibroblasts is reported. Blood lymphocytes of the patient have a normal karyotype. The origin of this tetrasomy 21 mosaicism is discussed.

Mosaic tetrasomy 21 in severe mental handicap

In this report we give a detailed description of the clinical and psychological follow-up data of three young 49,XXXXY males, paying special attention to changes in intellectual performance and behaviour at different ages.

The 49,XXXXY syndrome. Clinical and psychological follow-up data.

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