M.G.E.M. Ausems

Broad spectrum of Pompe disease in patients with the same c.-32-13T -> G haplotype

Background: Pompe disease (acid maltase deficiency, glycogen storage disease type II; OMIM 232300) is an autosomal recessive lysosomal storage disorder characterized by acid α-glucosidase deficiency due to mutations in the GAA gene. Progressive skeletal muscle weakness affects motor and respiratory functions and is typical for all forms of Pompe disease. Cardiac hypertrophy is an additional fatal symptom in the classic infantile subtype. c.-32-13T→G is the most common mutation in adults. Objective: To delineate the disease variation among patients with this mutation and to define the c.-32-13T→G haplotypes in search for genotype–phenotype correlations. Methods: We studied 98 compound heterozygotes with a fully deleterious mutation (11 novel mutations are described) and the common c.-32-13T→G mutation. Results: All patients were Caucasian. None had the classic infantile form of Pompe disease. The clinical course varied far more than anticipated (age at diagnosis <1 to 78 years; age at onset: <1 to 52 years). The acid α-glucosidase activities in a subset of patients ranged from 4 to 19.9 nmol/mg/h. Twelve different c.-32-13T→G haplotypes were identified based on 17 single-nucleotide polymorphisms located in the GAA gene. In 76% of the cases, c.-32-13T→G was encountered in the second most common GAA core haplotype (DHRGEVVT). In only one case was c.-32-13T→G encountered in the major GAA core haplotype (DRHGEIVT). Conclusion: Patients with the same c.-32-13T→G haplotype (c.q. GAA genotype) may manifest first symptoms at different ages, indicating that secondary factors may substantially influence the clinical course of patients with this mutation.

A diagnostic protocol for adult-onset glycogen storage disease type II

Article abstract To analyze the diagnostic value of various laboratory tests for the confirmation of adult-onset glycogen storage disease type II (GSD II), we performed a clinical, biochemical, and genetic study of 18 patients with this disease. Measurement of acid α-glucosidase (GAA) activity in muscle and histopathologic analysis of muscle tissue appeared to have no additional value when GAA activity in leukocytes was clearly deficient. Our study showed that creatine kinase elevation is a sensitive marker of GSD II. A diagnostic protocol is formulated.

Glycogen storage disease type II: birth prevalence agrees with predicted genotype frequency

Objectives: To compare the overall birth prevalence of diagnosed glycogen storage disease type II (GSD II) with the predicted frequency based on mutation screening, in order to determine whether GSD II is an underdiagnosed condition, and to analyze which medical disciplines recognize GSD II. Methods: Retrospective data on all enzymatic diagnoses of GSD II were collected from diagnostic labs throughout the Netherlands, covering the period from January 1, 1972 to December 31, 1996. Age-specific diagnostic incidence rates were calculated for the entire study period. By adding together the diagnostic incidences for all age groups, we calculated the birth prevalence of diagnosed GSD II and compared these figures with the predicted frequency based on mutation screening in a random sample from the general population. The medical specialization of the referring clinicians was also recorded. Results: GSD II was diagnosed in 154 individuals, including 11 prenatal diagnoses. The birth prevalences of the various phenotypes were 1/101,000 (infantile form), 1/720,000 (juvenile form) and 1/53,000 (adult form). The birth prevalence of the adult and infantile phenotype together was 1/35,000. Eighty-two percent of the patients were diagnosed in university hospitals. Of the patients with infantile GSD II, 71% were diagnosed by a pediatrician, whereas most patients with adult GSD II were diagnosed by a neurologist (80%). Conclusions: There is no evidence for the underdiagnosis of GSD II in the Netherlands, as the calculated birth prevalences of the disease are consistent with previous predictions based on mutation screening in a random sample of newborns. The worldwide birth prevalence of the disease may well be higher than 1 in 100,000. GSD II is mainly diagnosed in university hospitals.

Different phenotypic expression in relatives with Fabry disease caused by a W226X mutation

Two male relatives with Fabry disease presented striking differences in clinical symptoms and age of onset. The propositus had retarded statural growth and skeletal dysplasia while his nephew suffered mainly from aggravating acroparesthesia and celiac disease. Fabry disease is an X-linked inborn error of glycosphingolipid metabolism resulting from deficient activity of the lysosomal hydrolase alpha-galactosidase A (alpha-Gal A) enzyme. The alpha-Gal A gene is located at Xq22.1. Efforts to establish genotype-phenotype correlations have been limited because most patients have private mutations. In previous clinical studies performed in families with Fabry disease, marked differences in phenotype are described between affected relatives. This family also demonstrates the difficulty in predicting the clinical phenotype in patients and relatives with the same alpha-Gal A mutation. Furthermore, in the absence of a family history, the diagnosis may be easily missed.

Impact of rapid genetic counselling and testing on the decision to undergo immediate or delayed prophylactic mastectomy in newly diagnosed breast cancer patients: findings from a randomised controlled trial

Background:Female breast cancer patients with a BRCA1/2 mutation have an increased risk of contralateral breast cancer. We investigated the effect of rapid genetic counselling and testing (RGCT) on choice of surgery.Methods:Newly diagnosed breast cancer patients with at least a 10% risk of a BRCA1/2 mutation were randomised to an intervention group (offer of RGCT) or a control group (usual care; ratio 2 : 1). Primary study outcomes were uptake of direct bilateral mastectomy (BLM) and delayed contralateral prophylactic mastectomy (CPM).Results:Between 2008 and 2010, we recruited 265 women. On the basis of intention-to-treat analyses, no significant group differences were observed in percentage of patients opting for a direct BLM (14.6% for the RGCT group vs 9.2% for the control group; odds ratio (OR) 2.31; confidence interval (CI) 0.92–5.81; P=0.08) or for a delayed CPM (4.5% for the RGCT group vs 5.7% for the control group; OR 0.89; CI 0.27–2.90; P=0.84). Per-protocol analysis indicated that patients who received DNA test results before surgery (59 out of 178 women in the RGCT group) opted for direct BLM significantly more often than patients who received usual care (22% vs 9.2%; OR 3.09, CI 1.15–8.31, P=0.03).Interpretation:Although the large majority of patients in the intervention group underwent rapid genetic counselling, only a minority received DNA test results before surgery. This may explain why offering RGCT yielded only marginally significant differences in uptake of BLM. As patients who received DNA test results before surgery were more likely to undergo BLM, we hypothesise that when DNA test results are made routinely available pre-surgery, they will have a more significant role in surgical treatment decisions.

Asymptomatic and late-onset ornithine transcarbamylase (OTC) deficiency in males of a five-generation family, caused by an A208T mutation.

In a large five‐generation Polish family, late‐onset ornithine transcarbamylase (OTC) deficiency in males segregated with the missense mutation Ala208Thr (A208T), and all heterozygous females were asymptomatic. No other mutations were found in the coding sequences and intron‐exon boundaries of the OTC gene. Surprisingly, the mutation originated from the great‐grandfather of the index patient who died at age 59 of liver carcinoma. He never had dietary restrictions or hyperammonemic spells throughout life and appears to be the oldest male reported with OTC deficiency. The index patient had a severe OTC deficiency (3% of normal). Eight males died suddenly at ages 4 months to 23 years (average 14 years) after a foudroyant episode triggered by a common infection. The patients remained undiagnosed for 28 years because a metabolic defect was not considered to be the cause of the acute episodes. Recognition of the familial pattern of inheritance was initially unnoticed since the patients were admitted to eight different hospitals. DNA analysis predicted that two ‘healthy’ boys also had OTC deficiency, which was confirmed by abnormal results of allopurinol challenge tests. Initial suspicion of OTC deficiency in such families is complicated, since symptoms can develop at any age, or even remain absent. This obscures the typical pattern of X‐linked inheritance in small families.

Who is being referred to cancer genetic counseling? Characteristics of counselees and their referral.

Both physician and patient play a role in the referral process for cancer genetic counseling. Access to such counseling is not optimal because some eligible patients are not being reached by current referral practice. We aimed to identify factors associated with the initiator of referral. During a 7-month period, we recorded demographic characteristics like gender, personal and family history of cancer, ethnicity and eligibility for genetic testing for 406 consecutive counselees using a specially designed questionnaire. Counselees were seen in a university hospital or a community hospital (n = 7) in the Netherlands. We also recorded educational level of each counselee, clinical setting and who initiated referral. Descriptive statistics were used to describe the counselees’ general characteristics. We analysed the association between counselee characteristics and the initiator of referral by logistic regression. The majority of counselees seemed to have initiated referral themselves but were indeed eligible for genetic testing. In comparison to the general population in the Netherlands, the counselees had a higher level of education, and there were fewer immigrants, although a higher level of education was not found to be a facilitating factor for referral. The clinical setting where a counselee was seen was associated with initiator of referral, although this relationship was not straightforward. There is a complex interaction between clinical setting and initiator of referral, which warrants further research to elucidate the factors involved in this relationship. Patients seen in cancer genetic counseling do not reflect the general population in terms of educational level or ethnicity.

Homozygous deletion of exon 18 leads to degradation of the lysosomal alpha-glucosidase precursor and to the infantile form of glycogen storage disease type II.

We describe two unrelated Dutch patients with typical symptoms of infantile glycogen storage disease type II (GSD II) and virtual absence of acid α‐glucosidase activity in leukocytes and cultured skin fibroblasts. The patients were identified as homozygotes for a deletion of exon 18 of the acid α‐glucosidase gene (GAA). The in‐frame deletion manifests at the protein level in a characteristic way: the enzyme precursor is smaller than normal and degraded in the endoplasmic reticulum or Golgi complex. These cases present an evident example of a genotype‐phenotype correlation in glycogen storage disease type II.

Abstract P4-11-01: Rapid genetic counseling and testing in newly diagnosed breast cancer patients, findings from an RCT

Introduction: Female breast cancer patients carrying a BRCA1/2 mutation have an increased risk of second primary breast and ovarian tumors. Rapid genetic counseling and testing (RGCT) may aid in making informed decisions about therapeutic and preventive surgery and adjuvant treatment. Little is known about the effects of RGCT on treatment decisions and psychosocial well-being. We have performed a randomized controlled trial to investigate these issues. Methods: Newly diagnosed breast cancer patients from 12 Dutch hospitals with at least a 10% risk of carrying a BRCA1/2 mutation were randomized to an intervention group (RGCT) or a usual care control group (ratio 2:1). Study outcomes included uptake of RGCT, choice of type of surgery, cancer risk perception, cancer-specific distress, quality of life and decisional satisfaction. Assessments took place at study entry, and at 6 and 12 months follow-up. Results: Between 2008 and 2010, 271 patients were recruited, of whom 3 subsequently withdrew. The remaining 268 patients were randomized to the intervention (n = 181) or control (n = 87) group. Complete questionnaire data were available for 250 (93%) and 243 (91%) patients at 6 and 12 months follow-up, respectively. Of the 181 women in the intervention group, 180 (98%) underwent genetic counseling after a median of 4 days. One-hundred thirteen (63%) of them opted for accelerated DNA test procedures, of whom 72 underwent rapid testing (results available in Conclusion: The uptake of rapid genetic counseling among high-risk breast cancer patients was high, and the majority of patients underwent accelerated DNA-testing procedures. However, RGCT did not have a significant effect on choice of type of primary surgery. In part, this may be explained by the fact that surgeons and patients often did not wait for DNA test results before primary surgery. Conclusions regarding the psychosocial impact of RGCT will be presented at the time of the conference. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P4-11-01.

Report on the Second National Conference on Genetics and Public Health

Abstracts Community Genet 1999;2:119–136 121 Plenary Sessions Community Genet 1999;2:119–136 121 Plenary Session