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Diamond Blackfan anaemia in the UK: clinical and genetic heterogeneity.

A detailed family study was undertaken of patients notified to the UK Diamond Blackfan Anaemia (DBA) Registry. RPS19 mutations were detected in 16 of 104 families, including two patients with deletions detected by intragenic loss of heterozygosity of tightly linked polymorphisms. In two further cases, polymorphisms were used to determine the parental allele of origin of RPS19 point mutations. A review of clinical details of patients with mutations and patients in the literature having identical or equivalent mutations revealed evidence for a genotype:phenotype correlation with respect to the prevalence of physical anomalies, and the occurrence of mild or variable haematological severity. Nine of 60 patients had a known family history of DBA. Haematological abnormalities, including raised red cell adenosine deaminase activity, were found in first-degree relatives of 16 of 51 (31%) of patients not previously considered to have familial DBA. Results of both parents and any siblings were normal in only 35 of 60 (58%) of cases, who were therefore assumed to have sporadic de novo DBA. The classical inheritance pattern for DBA is autosomal dominant; however, 12 of 60 families (20%) had more than one affected child despite normal results in both parents. These results have important implications for genetic counselling, and for the selection of potential sibling bone marrow donors.

Adult↗

Familial multiple blue naevi.

Blue naevi are benign melanocytic neoplasms. They are usually solitary blue or blue-black nodules or plaques. Multiple blue naevi have been reported rarely and there is one report of familial solitary blue naevus. However, familial multiple blue naevi have not been reported previously. We report the case of a family with multiple blue naevi occurring in three generations with an autosomal-dominant inheritance pattern.

Female↗

Three cases of focal dermal hypoplasia (Goltz syndrome).

Focal dermal hypoplasia or Goltz syndrome is a rare genodermatosis, characterized by multiple abnormalities of ectodermal and mesodermal origin. It is found predominantly in females and is characterized by hypoplasia of skin and papillomas. Three cases of focal dermal hypoplasia in infancy with unusual inheritance patterns are reported. Cutaneous features were atrophic reticulated scars involving the trunk and extremities following the lines of Blaschko. Papillomas were present on the genitalia and in a periorificial distribution. Skeletal abnormalities included syndactyly, polydactyly and lobster claw deformities. Ophthalmological examination revealed strabismus and retinal colobomas.

Eye Abnormalities↗

Linkage of IgA deficiency to Gm allotypes; the influence of Gm allotypes on IgA-IgG subclass deficiency.

IgA deficiency (IgAD) is the most common immunodeficiency, characterized by an arrest in B cell differentiation. It has a sporadic occurrence or variable inheritance pattern, and is also linked to the HLA genes. IgA deficiency is sometimes associated with IgG subclass deficiency. In this study the Gm allotypes, as genetic characteristics of the IgG1, IgG2 and IgG3, were analysed in 83 Caucasian IgAD individuals. Half of the patients presented with IgG4 < 0.01 g/l compared with 5% (P < 0.001) in a healthy population. Three of the 83 had significantly low IgG2 and four had significantly low IgG3 levels. Gm allotype frequencies in IgAD deviated compared with a normal population. Of the 83 patients, 44 (53%) showed homozygous G2 m(",") expression on the IgG2 locus (33% in controls, P < 0.01). In IgAD the Gm(a,",g) haplotype was more frequent (43%) compared with controls (31%, P < 0.01). The Gm homozygous phenotype Gm(a,",g/a,",g) was most common, found in 20 of 83 patients (24%, P < 0.05) compared with controls (14%). On the other hand the Gm(f,n,b) haplotype of IgAD was rare (28%) compared with controls (45%, P < 0.001). The low IgG4, < 0.01 g/l, found in 50% of the patients, was even more frequent (56-69%) among the G2 m(",") phenotypes. IgG subclass levels were given for different Gm phenotypes of the IgAD group and compared with controls. Significantly low IgG4 was revealed in the Gm(a,",g/a,",g) phenotype (P < 0.01) and significantly low IgG2 in the Gm(a,",g/f,",b) phenotype (P < 0.01). The Gm(a,",g/f,",b) phenotype contained the three patients found with IgG2 levels < -2 s.d., and the four patients with IgG3 levels < -2 s.d. were present among those with the homozygous Gm(a,",g/a,",g) phenotype; both phenotypes with G2 m(",") on the IgG2 locus. The 'compensatory' increase of IgG was significant for both IgG1 and IgG3 in all Gm phenotypes, but in the Gm(a,",g/f,",b). Thus, the susceptibility of IgAD with the additional IgG antibody deficiencies, down-regulated IgG4 and IgG2/IgG3, is associated with Gm allotypes, especially the homozygous G2 m(",") expression on the IgG2 locus.

Hemagglutination Inhibition Tests↗

Multiple endocrine neoplasia 2A due to a unique C609S RET mutation presents with pheochromocytoma and reduced penetrance of medullary thyroid carcinoma.

OBJECTIVE: We have identified a large kindred with multiple endocrine neoplasia 2A (MEN 2A) due to a mutation at RET codon 609 that results in a cysteine to serine substitution, a mutation previously identified in only one case in the literature. We characterized the clinical phenotype of the kindred and the biochemical mechanism of this new mutation. PATIENTS AND DESIGN: The index case, a 42-year-old woman, presented with pheochromocytoma. We screened 29 family members for the presence of the mutation. Of the 15 mutation-positive family members, 11 agreed to undergo further evaluation by physical examination, calcium and pentagastrin-stimulated calcitonin levels, measurement of urinary metanephrines, adrenal imaging and serum calcium levels. Biochemical characterization of the mutation was by transient transfection of human neuroblastoma cells and Western blot analysis. RESULTS: This kindred demonstrated an inheritance pattern consistent with autosomal dominant pheochromocytoma. Strikingly, no clinically evident case of medullary thyroid cancer (MTC) was observed among mutation-positive family members. Thyroidectomy in six cases revealed C-cell hyperplasia in all and microscopic MTC in two cases. Transfection experiments using human neuroblastoma cells showed that the mutant RET, unlike the wild-type receptor, is constitutively phosphorylated in the absence of ligand, and thus resembles other previously characterized MEN 2A mutations. CONCLUSIONS: The identification of a new mutation causing a MEN 2A phenotype that features pheochromocytoma and the surprising absence of clinically apparent MTC has significant implications for carriers of this mutation and provides further insights into the genotype-phenotype correlation in MEN 2A.

Adolescent↗

Clinical and cytogenetic survey of institutionalized mentally retarded patients with emphasis on the fragile-X syndrome.

A detailed clinical and cytogenetic survey for the fragile-X syndrome was undertaken on 201 institutionalized mentally retarded males with no previously recognized cause of retardation, and the causes of mental retardation were summarized from a total of 595 institutionalized male and female patients after the review of their medical records including clinical and cytogenetic data. Among the 201 males clinically and cytogenetically examined, five (2.5%) had abnormal chromosome findings with four (2%) having the fragile-X syndrome. Twelve of the males (6.0%) were diagnosed with a single gene disorder. In the present study, mental retardation was classified as possibly due to multifactorial causes when a genetic syndrome, chromosome abnormality or environmental insult was not identified, but mental retardation was present in one or more first and/or second degree relatives, but did not follow a recognizable inheritance pattern. Hence, mental retardation was recorded in other family members and may indicate possible multifactorial causes in 45 males (22.4%). An environmental insult was noted in 25 males (12.4%); unexplained birth defects in three males (1.5%); a specific condition or diagnosis identified, but cause unknown (e.g. Rubinstein-Taybi syndrome) in 10 males (5%); and no diagnosis made in the remaining 101 males (50.2%). Of all 595 patients (334 males and 261 females), including the 201 males who had undergone a detailed clinical and cytogenetic evaluation, 39 (6.6%) had abnormal chromosome findings, with Down's syndrome noted in 31 of the patients. Twenty-five patients (4.2%) were diagnosed with a single gene disorder while mental retardation was noted in other family members and may indicate possible multifactorial causes in 64 patients (10.8%). An environmental insult was noted in 170 patients (28.6%); unexplained birth defects in 17 patients (2.9%); a specific condition or diagnosis but cause unknown in 27 patients (4.5%); and no diagnosis made in 253 patients (42.5%). Clinical and cytogenetic screening of mentally retarded patients for the fragile-X syndrome and other causes of mental retardation is helpful in identifying individuals and their families who may benefit from genetic services such as counseling and treatment. This study was performed over an approximate 2 year period from 1987 to 1989.

Adolescent↗

The Malmö biomarker programme.

Evaluation of pro-oxidant/antioxidant dietary factors in relation to individual susceptibility to cancer and cardiovascular disease is justified based on a review of the literature. This working hypothesis is amendable to further scientific validation from biomarkers with end-point sensitivity to oxygen radicals. So far, the biomarker programme developed around this theme may be divided into three distinct classes: (1) Markers of genotoxic exposure estimate DNA damage either directly as a biologically effective dose, or indirectly by estimating aberrant cellular functions that lead to accumulation of DNA damage. The examples included are ADP-ribosylation in mononuclear leucocytes (R. Pero, A. Olsson), oxidative DNA damage (K. Frenkel), gene expression in lymphocytes (S. Garte, G. Cosma), serum alpha macroglobulin (W. Troll) and oxidized DNA damage and repair (N. Christie). (2) Markers of genetic predisposition have been shown to have genetic inheritance patterns that relate to individual susceptibility to cancer or cardiovascular disease. The examples included are glutathione transferase mu phenotyping (R. Pero, J. Seidegård) and poly (ADP-ribose) polymerase pseudogene polymorphism (M. Smulson). (3) Markers of dietary status have been validated to estimate the amount of a particular nutrient or xenobiotic in the diet that has been taken up and metabolized or distributed to body fluids or tissues. The example included here is niacin nutriture (E. Jacobson, M. Jacobson). This biomarker is presented in Section 5 (pp. 59-62) of the Malmö Diet and Cancer Programme Minisymposium reported in this issue of the journal.

Animals↗

Genetics of the GPT system. Family, mother/child and association studies.

GPT types are presented for 150 Norwegian matings, with 454 children, and 1703 Norwegian mother/child combinations. There were five exceptions to a simple codominant inheritance pattern, all believed to be due to a segregating Gpt-0-allele. Rare phenotypes were encountered in two of the families and in 11 of the mother/child combinations. Compiled family material and mother/child material are presented. No indication of association was found between GPT types and phenotypes within the ABO, Rh, MN, Hp, Gc, C3, PGM1, and ACP1 systems. There is a marked association between EBS-Ogna (epidermolysis bullosa simplex, type Ogna) affection and GPT phenotypes. This reflects the Gpt-EBS1 linkage phase. No evidence was found of association between GPT phenotypes and either nephrological diseases or PKU (phenylketonuria).

Alanine Transaminase↗

The oro-facial-digital syndrome.

Two patients, a mother and her daughter, are presented who manifest the clinical features of the oro-facial-digital syndrome (OFD I). Many of these features are shared with Mohr's syndrome (OFD II). Confusion arises when a patient presents with features common to both syndromes. The features which are always or sometimes associated with these syndromes are tabulated. The Tables also show which abnormalities are common to both syndromes and to our cases. Additional clinical and radiological features which have not been considered part of these syndromes are described. We present these cases to suggest that these syndromes should be "lumped" together as one syndrome. We propose expanding this syndrome to include ear and renal abnormalities. Our cases follow an X-linked dominant inheritance pattern and, therefore, do not help determine the genetic controversy of these two syndromes.

Abnormalities, Multiple↗

Counseling for dominant traits: a correction for the ascertainment bias due to referral for analysis.

Genetic heterogeneity complicates genetic counseling because the correct mode of inheritance must be determined independently for each pedigree. When autosomal and X-linked dominants inheritance mechanisms are known, as for example with retinitis pigmentosa, then only families where male-to-male transmission is observed may be readily counseled. The other pedigrees may be autosomal but lack male-to-male transmission due to chance segregation. Since only the pedigrees without male-to-male transmission are analyzed for their mode of inheritance, there is an ascertainment bias which must be corrected when evaluating the likelihood of the two inheritance patterns. A method to correct for this bias using conditional likelihoods is given, along with examples to demonstrate its use.

Female↗

Albinism in Nigeria with delineation of new recessive oculocutaneous type.

Seventy-nine Nigerian oculocutaneous albinos were investigated. Fifty-six had typical tyrosinase-positive albinism (TPA) and 23 had brown albinism (BA), a new oculocutaneous type. The TPA were characterized by localized but no generalized skin pigment, yellow hair, blue to brown irides, nystagmus, and reduced or absent retinal pigment. Localized skin pigment included freckles and lentigines. The iris and skin pigment were the result of the slow accumulation of pigment with age as both were found in older individuals. The most severe skin changes were premalignant keratoses and squamous cell carcinoma of the skin, and the skin malignancies were the major factor in limiting the lifespan for TPA. The BA were characterized by generalized light brown skin pigment, light brown hair, blue to brown irides, nystagmus, and reduced retinal pigment. There was little accumulation or change of pigment in the eyes or skin with age. The generalized light skin pigment was effective in reducing sensitivity to solar radiation and very few BA had premalignant keratoses. Pedigree analysis for BA suggested on autosomal recessive inheritance pattern.

Adolescent↗

Genetic counseling for autosomal dominant diseases with a negative family history.

The first appearance of an autosomal dominant disease in a family is often attributed to new mutation, and the parents may be given a very low risk of recurrence for future offspring. This counseling is not appropriate if penetrance of the disease is incomplete and the reproductive fitness of affected individuals is close to normal. The risk of recurrence (PR) for an autosomal dominant disease in the sibling of an affected child, neither of whose parents is affected, may be estimated as: (Formula: see text) where f is fitness of the carrier genotype regardless of phenotype, y is penetrance, and mutation-selection equilibrium is assumed to exist. Recurrence risks have been calculated with this formula for various values of f and y. In cases in which penetrance is moderate and fitness is moderate or high, the risk of recurrence in siblings of the proband is often greater than 10%. When fitness is very high (f greater than 0.9), the risk to siblings may be greater than 25%. These observations have important implications for genetic counseling and may also affect mutation rate calculations, demonstration of paternal age effects, and determination of inheritance patterns in genetically heterogeneous conditions.

Genes, Dominant↗

Robinow syndrome: report of two patients and review of literature.

We report two patients with Robinow or fetal face syndrome. We present a thirteen year follow-up on three previously published cases and a review of 32 cases in the literature. The cardinal features of this condition include mesomelic shortening of the forearms, frontal bossing, hypertelorism, wide palpebral fissures, short upturned broad nose with anteverted nares, long philtrum, small chin, brachydactyly, hypoplastic genitalia and a normal karyotype. Development delay and mental retardation was noted in 18% of the reported cases. Early death was identified in about 10% of the cases. Genetic heterogeneity is suggested with autosomal dominant inheritance reported in 8 individuals from 3 families and autosomal recessive inheritance in 8 siblings from 4 families although no clinical differences were identified among those individuals with different inheritance patterns. Male to male transmission was reported in one family. Parental age does not appear to be a factor in the cause of this syndrome.

Abnormalities, Multiple↗

Hereditary spastic diplegia with mental retardation in two young siblings.

Two young siblings with hereditary spastic diplegia and mental retardation (Böök's syndrome) have had detailed clinical investigations since infancy. The inheritance pattern of this syndrome in the present family fits well with an autosomal recessive trait--with affected sibs of opposite sex, born to consanguineous healthy parents.

Abnormalities, Multiple↗

Further evidence of genetic heterogeneity in hereditary hydronephrosis.

Hereditary hydronephrosis is a rare condition but several families are described in the literature. The inheritance pattern is autosomal dominant (McKusick number 143400) but the exact aetiology of the hydronephrosis is not clear. However, linkage with the HLA region on chromosome six has been shown previously. We report a family not showing linkage to this region, giving further evidence of genetic heterogeneity in this condition.

Adolescent↗

HLA--determination in families with hereditary ataxia.

In three families with hereditary ataxia, where the inheritance pattern was autosomal and dominant, HLA antigens were determined in 25 members. In two of the families, HLA linkage of disease was suggested, whereas in the third family, the data did not directly support this concept, since two recombinational events between the postulated locus for disease and the HLA region had to be assumed. However, with this assumption, our data are compatible with those of one family described recently (Jackson et al. 1977) implying the presence on the sixth chromosome, outside the HLA region, of a locus that determines the development of spino cerebellar ataxia (SCA). Further tests with definition of enzyme markers will have to be performed before conclusions as to HLA linkage of a postulated SCA gene can be made.

Adolescent↗

Interaction between HLA antigens and immunoglobulin (Gm) allotypes in susceptibility to type I diabetes.

HLA-A,B,C and DR typing was performed on 108 Caucasian type I diabetic patients, 68 being Gm typed. The expected association with B8, B18, Bw62, DR3 and DR4 was observed as well as an excess of DR3/4 heterozygotes. DR2 was decreased in frequency. In the total patient group, no Gm association was observed but when the patients were subgrouped according to HLA type, HLA/Gm interactive effects were seen. An increase in Gm(1,3;5) was observed in DR3 positive, DR4 negative patients. This association occurred predominantly in females (compared with DR4 and DR3/4 patients of the same Gm phenotype who were predominantly male). Further genetic heterogeneity was identified within DR3/4 patients. Within this group, Bw62 was increased (strongly suggestive of Bw62-DR4 haplotypes) within B8, Gm heterozygotes compared with B8, Gm homozygotes. This finding can be interpreted as indicating a three-way interaction between genes on two HLA haplotypes and Gm-linked genes. These results reflect the genetic heterogeneity and complexity of insulin-dependent diabetes mellitus and explain in part the previous failure of simple genetic models to adequately explain inheritance patterns observed.

Diabetes Mellitus, Type 1↗