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Mutations in the transporter ABCA12 are associated with lamellar ichthyosis type 2.

Lamellar ichthyosis type 2 (LI2) is a rare autosomal recessive skin disorder for which a gene has been localized on chromosome 2q33-35. We report the identification of five missense mutations in the ABCA12 gene in nine families from Africa affected by LI2. The mutations were homozygous in eight consanguineous families and heterozygous in one non-consanguineous family. Four of these mutations are localized in the first ATP-binding domain (nucleotide-binding fold), which is highly conserved in all ABC proteins. The ABCA12 protein belongs to a superfamily of membrane proteins that translocate a variety of substrates across extra- and intracellular membranes. ABCA transporters have been implicated in several autosomal recessive disorders, notably of lipid metabolism. By analogy with ABCA3, a lamellar body membrane protein in lung alveolar type II cells, ABCA12 could function in cellular lipid trafficking in keratinocytes.

Black People↗

L-2-Hydroxyglutaric aciduria: identification of a mutant gene C14orf160, localized on chromosome 14q22.1.

l-2-Hydroxyglutaric aciduria (l-2-HGA) is characterized by progressive deterioration of central nervous system function including epilepsy and macrocephaly in 50% of cases, and elevated levels of l-2-hydroxyglutaric acid in urine, blood and cerebrospinal fluid (CSF). Nuclear magnetic resonance imaging shows distinct abnormalities. We report the identification of a gene for l-2-HGA aciduria (MIM 236792) using homozygosity mapping. Nine homozygous mutations including three missense mutations, two nonsense mutations, two splice site mutations and two deletions were identified in the gene C14orf160, localized on chromosome 14q22.1, in 21 patients from one non-consanguineous and 14 consanguineous Turkish families. We propose to name the gene duranin. Duranin encodes a putative mitochondrial protein with homology to FAD-dependent oxidoreductases. The functional role of this enzyme in intermediary metabolism in humans remains to be established.

Adolescent↗

Antenatal Bartter syndrome with sensorineural deafness: refinement of the locus on chromosome 1p31.

BACKGROUND: Recently a locus for antenatal Bartter syndrome associated with sensorineural deafness was mapped to human chromosome 1p31 in a single consanguineous Bedouin family (Brennan et al. Am J Hum Genet 1998; 62: 355-361). METHODS: By haplotype analysis we demonstrate linkage to this locus in nine consanguineous families with antenatal Bartter syndrome associated with sensorineural deafness. RESULTS: The critical interval compatible with linkage was refined to 4.0 cM by two novel recombinational events with markers D1S2661 and D1S475. CONCLUSION: We thereby confirmed this gene locus and distinguished this clinical subtype from other variants of Bartter syndrome as a new disease entity.

Bartter Syndrome↗

Screening programme for phenylketonuria in the Gaza Strip: evaluation and recommendations.

Phenylketonruia (PKU) is an inherited metabolic disorder that results in progressive mental retardation. PKU is a paradigm of a disease that can be identified by proper screening of newborns and medical follow-up in order to prevent serious complications. The present study was designed to evaluate the Palestinian national screening programme for PKU in the Gaza Strip. Data about the screening of PKU in the Gaza Strip were obtained from the records of the healthcare centers of the Palestinian Ministry of Health (MOH) during the year 2000. In addition, PKU patients and families were interviewed. The results showed that the prevalence of PKU in the Gaza Strip varied considerably between the different regions with an overall prevalence of 6.35/100,000, while the maximum prevalence of 28.3/100,000 occurred in the rural areas. Coverage of PKU testing in the Gaza Strip is limited to about 35.3 per cent of the total newborns, who are delivered and receive health care at the government clinics. Among those newborns delivered at the government clinics, the percentage of PKU screening is about 87.8 per cent. However, PKU testing is not carried out at UNRWA clinics where about two-thirds of newborn deliveries take place. On average, 61 per cent of PKU testing is made in the infant's second week, ranging between 11 and 17 days, and the remaining (39 per cent) are tested thereafter. Approximately 60 per cent of PKU patients had consanguine parents (first cousins), while 7.7 per cent had no consanguinity. Only 43.1 per cent of PKU patients were fed on the specialized low phenylalanine milk. An inverse correlation was reported between the use of low phenylalanine milk and age. A total of 35.4 per cent of the PKU patients were regularly monitored by blood tests each month, 47.7 per cent had not been tested for the previous year. It was concluded that the PKU screening programme has to be improved, the screening methods should be reviewed, and the screening coverage should include all the newborns in the Gaza Strip.

Consanguinity↗

Homozygous protein C deficiency with a double variant His 202 to Tyr and Ala 346 to Thr.

We present the protein C gene analysis of a patient with homozygous protein C deficiency. The patient was referred with purpura fulminans 3 h after birth. Skin necroses had developed on the scalp, abdomen and upper extremities when he was two days old. His protein C activity was 0.03-0.05 IU/ml and the levels in his consanguineous parents were 0.32 and 0.40 IU/ml. He was treated initially with fresh frozen plasma, and later with daily oral anticoagulants, for two episodes of skin necrosis. He had three more episodes of skin necroses that were treated with intravenous protein C concentrate. He is now two years old and under treatment with daily coumarin 0.1-0.2 mg/kg per day to keep the International Normalized Ratio between 2.0-4.5. DNA analysis showed that he is homozygous for a double variant bearing His 202 to Tyr and Ala 346 to Thr mutations. His parents were each heterozygous for the double variant and were consanguineous. This mutation has been reported previously in an Austrian patient but this is the first homozygous case for this double variant.

Alanine↗

Nevo syndrome.

We describe a male patient born to consanguineous parents with a syndrome of tall stature at birth, hypotonia, wrist drop and long spindle shaped fingers. The clinical features are identical to those previously described in three cases from a single family by Nevo et al. (1974: J Med Genet 11: 158-165). Autosomal recessive inheritance is supported by consanguinity in our case. Follow-up at age 3 years demonstrated significant improvement of hypotonia and motor function, and normal cognitive ability.

Body Height↗

Transposition of external genitalia and associated malformations.

We report three Egyptian boys from three different families born with penoscrotal transposition (PST). None of them fell into categories of known syndromes, associations, sequences or chromosome disorders. Other malformations observed included renal, genital, cardiovascular and limb defects. Although the occurrence of most reported cases of PST are sporadic, three families with affected sibs have been reported in the literature where parental consanguinity was not specified. Parental consanguinity is present in two of our three cases with young parental age suggesting the possibility of an autosomal recessive pattern of inheritance. A history of maternal hormonal treatment early in pregnancy in one of our cases may suggest a role of teratogenic agents. We conclude that PST may represent only a part of a wide spectrum of anomalies resulting from a major insult occurring during early embryonic development and is of heterogeneous etiology.

Abnormalities, Multiple↗

Bilateral corneal anesthesia associated with diaphragmatic paralysis, ovarian failure, and developmental delay.

PURPOSE: To describe two siblings with bilateral corneal anesthesia associated with multiple systemic abnormalities. DESIGN: Interventional case report. METHODS: A 38-year-old Hispanic woman was seen for bilateral corneal ulcers, exposure keratitis, hemorrhagic retinopathy, and multiple systemic abnormalities. A younger sibling with similar but milder findings was also examined. Medical and genetic evaluation was investigated in these two siblings with bilateral decreased sensation and multiple abnormalities from a consanguineous union. RESULTS: Examination of the patient showed bilateral corneal anesthesia, and multiple systemic abnormalities included diaphragmatic paralysis, ovarian failure, multiple thrombotic cerebrovascular accidents, pedal edema, mandibular hypoplasia, and developmental delay. Milder findings were seen in a sibling. Corneal ulcers were stabilized after treatment that included bandage contact lens, pressure patching, topical antibiotics, and tarsorrhaphy. CONCLUSIONS: The combination of corneal anesthesia and systemic abnormalities, with parental consanguinity, suggests an inherited syndrome.

Abnormalities, Multiple↗

Does heterozygosity estimate inbreeding in real populations?

Many recent studies report that individual heterozygosity at a handful of apparently neutral microsatellite markers is correlated with key components of fitness, with most studies invoking inbreeding depression as the likely underlying mechanism. The implicit assumption is that an individual's inbreeding coefficient can be estimated reliably using only 10 or so markers, but the validity of this assumption is unclear. Consequently, we have used individual-based simulations to examine the conditions under which heterozygosity and inbreeding are likely to be correlated. Our results indicate that the parameter space in which this occurs is surprisingly narrow, requiring that inbreeding events are both frequent and severe, for example, through selfing, strong population structure and/or high levels of polygyny. Even then, the correlations are strong only when large numbers of loci (~200) can be deployed to estimate heterozygosity. With the handful of markers used in most studies, correlations only become likely under the most extreme scenario we looked at, namely 20 demes of 20 individuals coupled with strong polygyny. This finding is supported by the observation that heterozygosity is only weakly correlated among markers within an individual, even in a dataset comprising 400 markers typed in diverse human populations, some of which favour consanguineous marriages. If heterozygosity and inbreeding coefficient are generally uncorrelated, then heterozygosity-fitness correlations probably have little to do with inbreeding depression. Instead, one would need to invoke chance linkage between the markers used and one or more gene(s) experiencing balancing selection. Unfortunately, both explanations sit somewhat uncomfortably with current understanding. If inbreeding is the dominant mechanism, then our simulations indicate that consanguineous mating would have to be vastly more common than is predicted for most realistic populations. Conversely, if heterosis provides the answer, there need to be many more polymorphisms with major fitness effects and higher levels of linkage disequilibrium than are generally assumed.

Computer Simulation↗

Primary hereditary ichthyoses in the Eastern Province of Saudi Arabia.

BACKGROUND: Of 10,455 new dermatology patients seen at the Dermatology Clinic of King Fahad Hospital of the University, Al-Khobar, Saudi Arabia, between January 1990 and December 1995, the epidemiologic and demographic features of 71 patients, each with a histopathologically confirmed diagnosis of one specific type of primary hereditary ichthyosis (PHI), have been reviewed. OBJECTIVE: To study and document the epidemiologic and demographic profiles of patients with PHI in the Eastern Province of Saudi Arabia. METHODS: From the outpatient department dermatology logbooks, 71 patients with PHI, from 10,455 new cases with different dermatologic problems seen during the 5-year period, were included in this study. Using specially designed protocol forms, epidemiologic and demographic data were extracted from the medical records of the patients, entered into a computer, and analyzed using the SPSS program. RESULTS: Seventy-one patients with PHI, 44 males and 27 females (ratio, 1.63 : 1), were seen at our Dermatology Clinic between January 1990 and December 1995. The occurrence rate of PHI in our clinic is 0.67%, i.e. approximately 7 per 1000 new cases. The clinical pattern of PHI was as follows: 31 patients (44.7%) with ichthyosis vulgaris (IV), 12 (16.9%) with X-linked recessive ichthyosis (XLRI), four (5.6%) with lamellar ichthyosis (LI), three (4.2%) with bullous ichthyosiform erythroderma (BIE), and 21 (29.6%) with nonbullous ichthyosiform erythroderma (NBIE). IV was most common, followed by NBIE. Parental consanguinity was high (approximately 85%), and the family history was positive in 53 of the 71 cases (75%). CONCLUSIONS: This preliminary study has attempted to document the epidemiologic patterns of PHI patients in Saudi Arabia and, to our knowledge, this is the first report of its kind in this country. We found a high rate of parental consanguinity, a high percentage of patients with a positive family history, and many siblings affected by the severest forms of PHI, namely NBIE, BIE, and LI, which accounted for 39.4% of all cases of PHI.

Adolescent↗

Genetic heterogeneity of congenital glaucoma.

Analysis of 126 families comprising 205 patients with congenital glaucoma demonstrates that in Gypsies this disease follows the pattern of autosomal recessive inheritance with complete penetrance, while in the non-Gypsy population, its mode of inheritance is most probably multifactorial. In Gypsy patients with congenital glaucoma, the eyes are always bilaterally affected, the onset of the disease is in the prenatal period, and its course is rather severe. The population frequency of the disease is extremely high (among Gypsies), and the consanguinity rate among parents is as high as 41%. In non-Gypsy patients, 26.6% of all cases are only unilaterally affected, and the course of the disease is generally milder with a later onset. The population frequency in a non-Gypsy population is much lower, the consanguinity rate is not increased, and an excess of males (1.55:1) is significant.

Consanguinity↗

Genital anomaly and cardiomyopathy: a new syndrome.

Two brothers, products of a consanguineous marriage, had severe hypoplastic genitalia and cardiomyopathy. These findings are similar to those of three other brothers of another consanguineous family who in addition had evidence of mental retardation. These five boys probably represent a previously undescribed syndrome of genetic origin but of poorly understood pathogenesis.

Child, Preschool↗

Inbreeding and schizophrenia.

The unique situation that the Norwegian 1891 census included information on consanguineous relation between spouses and that first admissions to psychiatric hospitals by diagnosis were available for the years 1921-40, formed the basis for the present study. There are similarities between the pattern of inbreeding and admission rates in our rural communities, but we were unable to demonstrate any significant correlation. This is interpreted as due to selective avoidance in the choice of a marriage partner, particularly between near relatives. Good neighbourhood knowledge was an important factor in our sparsely populated communities with a marriage pattern distinguished by extreme geographical proximity of residence of spouses. The considerably lower proportion of first cousin matings than expected among parents of psychiatric in-patients 1926-55, illustrates the lower psychiatric morbidity in offspring of consanguineous parentage. Admissions 1921-40 comprised only functional psychoses with a predominance of schizophrenia (greater than 80%), which today is diagnosed in less than 10%. A decline in incidence rate is not likely, whereas changing diagnostic practice is probably a main factor. The near disappearance of catatonia and hebephrenia could be related to the introduction of psychotropic drugs and the accompanying improvement in hospital treatment. The epidemiology of schizophrenia is unchanged with a significant excess in lower social classes. This could in part be due to schizophrenic phenocopies related to the unchanged social differential in infant mortality and morbidity (including a particular season of birth effect), in part to the prevalence of adverse environment postnatally. The considerably greater male marital differential has probably a social cause, whereas male earlier onset of disease and more severe course of the disease are discussed in relation to the new concept of progressive sexual brain differentiation.

Adolescent↗

Clinical and genetic studies of muscular dystrophy in young girls.

During the years 1971-81, we treated 7 girls with clinical features suggestive of Duchenne dystrophy. Muscle weakness developed at 1.5 or at 5-8 years and progressed rapidly. Two girls were in wheel-chairs in their teens. Muscle atrophy began in the proximal parts of the lower extremities and pseudohypertrophy of the calf occurred in all patients. Serum creatine phosphokinase (CPK) activity was moderately to highly elevated in all cases and EMG showed a moderate to marked myopathic pattern. Chromosomal studies showed normal finding in the five examined. Mental retardation (IQ 37-73) was present in four. Consanguinity was present in 3 out of the 7 cases. Two mothers showed elevated levels of CPK and myopathic patterns on EMG. In addition, one mother had slight muscle weakness at the age of 42 and another had prominent pseudohypertrophy of the calf. Sex-linked recessive inheritance might be considered here, because carriers of autosomal recessive type never showed elevated levels of CPK or mild myopathic symptoms. The other five of our seven might be cases of autosomal recessive inheritance, because the mothers had normal serum CPK levels and in 2 families there was a consanguinity.

Adolescent↗

An epidemiological/genetic study of mental subnormality in Assiut Governorate, Egypt.

The aim of this investigation was to study the epidemiologic and genetic aspects of mental subnormality (MS) in Assiut Governorate, representing the Egyptian population. The sample comprised 3000 randomly selected subjects from three localities: one urban (Assiut City) and two adjacent rural villages. Age-matched controls were chosen for comparison. The Stanford-Binet test was administered to each individual. During history-taking special attention was paid to consanguinity and categorization on a genetic basis. The results revealed 116 cases with MS, showing an overall prevalence of 3.9%, which varied in the three locations: 3.4% in Assiut City, and 3.8% and 4.4% in the two rural locations. Clinico-genetic classification revealed the following: idiopathic MS 27.6%, MCA/MR syndromes 24.1%, primary CNS defect 12.9%, Martin-Bell syndrome 10.3%, inborn errors of metabolism 9.5%, tetratogenic and environmental causes 5.2%, MS and epilepsy 4.3%, chromosomal disorders 3.4% and MS associated with psychiatric disorder 2.6%. Parental consanguinity was found in 65% of the total sample, which emphasizes the role played by that factor in the etiology of mental subnormality in Egypt.

Adolescent↗

Retinitis pigmentosa in India: a genetic and segregation analysis.

Seventy-eight families with retinitis pigmentosa, presenting at the genetic clinic of Sankara Nethralaya, Madras, over a period of 6 months (from April to September 1993), were assessed to determine the different genetic types: 9% were autosomal dominant; 36%, autosomal recessive; 3%, X-linked recessive; 44%, isolated cases and 8%, undetermined genetic type. A high incidence of consanguinity was observed in autosomal recessive (57%) and isolated cases (37%). Segregation analysis showed good agreement in autosomal dominant (chi 2 = 0.864) and recessive families (p = 0.222). The high proportion of autosomal recessive and isolated cases in this study, when compared with other similar studies, is due to the high incidence of consanguineous marriages in the Indian subcontinent.

Consanguinity↗

Risk factors for mortality in young children living under various socio-economic conditions in Lahore, Pakistan: with particular reference to inbreeding.

Risk factors such as maternal age, parity, previous siblings' death, inbreeding of parents, birth weight, birth length were examined in a population-based prospective study in four population groups at different levels of urbanization in and round Lahore, Pakistan. From September 1984 to March 1995, 2967 full-term, single born infants were followed from the 5th month of gestation to 12 months of age. Logistic regression analysis showed a significant relative risk (RR) of infant death associated with parents' consanguinity (RR = 1.8), birth weight (RR = 1.8) and elder siblings' death (RR = 1.7). The risk attributed to these factors was 28, 17 and 25%, respectively. The number of lethal equivalents per gamete is about one. The B/A ratio 10.36 suggests that the genetic load is likely to be mutational. In countries like Pakistan, where consanguinity is favourably practiced, a substantial proportion of infant deaths may be prevented by cessation of such marriages. The implications of this finding for the Pakistani community are discussed.

Adolescent↗

Detection of RAG mutations and prenatal diagnosis in families presenting with either T-B- severe combined immunodeficiency or Omenn's syndrome.

It has been recently shown that mutations in both of the recombination activating genes RAG1 and RAG2 are involved in each of the two different types of severe combined immunodeficiency (SCID) syndromes: T-B- SCID and Omenn's syndrome (OS). The objective of the study was to search for novel mutations in the RAG genes and to offer prenatal diagnosis for families that have been identified as at risk of T-B- SCID or OS. Mutation analyses of polymerase chain reaction products of RAG1/RAG2 genes were performed in 14 cases (T-B- SCID = 6 and OS = 8). Consanguinity was reported in seven (50%) families. Four missense mutations in the RAG2 gene in six of eight OS patients and in four of six T-B- SCID patients were detected. The C1845T transition leading to a Tre215Ile substitution is a novel mutation. All but one of the patients were homozygous for the detected mutations, possibly reflecting the consanguinity in these families and the relative rarity of the disease-causing mutations. In addition, three putative polymorphic sites were found. Prenatal diagnosis was offered to seven families, but three of them declined genetic counseling for religious reasons. In the remaining families, four pregnancies were successfully completed, and in one case, the family chose to have an abortion because of a homozygous mutation. Mutations in RAG1/RAG2 genes were detected in only some of the T-B- SCID or OS patients, and the molecular basis for the remaining cases has yet to be elucidated. Important factors such as religious beliefs need to be considered when offering prenatal diagnosis to certain families.

Adult↗