Browsing by Author "Little, F"

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    Incidence of seropositive myasthenia gravis in Cape Town and South Africa
    (2007) Bateman, K J; Heckmann, J M; Little, F; Schinkel, M
    Background. Myasthenia gravis (MG) is a treatable autoimmune disease characterised by fatiguable weakness of skeletal muscles. More than 85% of MG patients have antibodies to the acetylcholine receptor (AChR) at the neuromuscular junction or are seropositive for MG (SPMG). In the developed world the incidence of MG has increased, particularly among older individuals, but no epidemiological studies have been done on SPMG in Africa. Objectives. To determine the annual incidence rate (IR) of SPMG in the Cape Town (CT) municipality, and the crude annual IR of SPMG for the whole of South Africa (SA). Methods. Positive AChR antibody tests were identified between 1 January 2003 and 1 January 2005 for patients living in CT, and the age- and sex-specific incidences were calculated. To determine the national crude annual IR over the same period, positive assays were identified from the laboratories that process AChR assays for SA. National Census 2001 population statistics formed the denominators. Results. There were 65 positive assays in CT, and 230 nationwide. Based on these figures the annual IR for CT was 11.2 per million per year (95% confidence interval (CI) 8.7 - 14.3), and for South Africa 2.6 per million / year (95% CI 2.2 - 2.9). After a questionnaire response from CT neurologists regarding the routine use of the AChR antibody assay, the annual IR for CT was adjusted to 12.6 per million (95% CI 9.9 - 15.9) to incorporate those presumed to have SPMG without a confirmatory test. In CT, the IR in females was 15.3 per million / year (95% CI 11.2 - 20.4), and in males, 6.8 per million / year (95% CI 4.1 - 10.7). The CT IRs for blacks, coloureds and whites were not statistically different after adjusting for age and gender. The IR of SPMG in CT was 6 times greater in those presenting after the age of 50 years than in those with earlier disease onset (95% CI 3.7 - 9.7). Conclusions. The annual IR of SPMG in CT is much the same as rates recorded recently in other developed countries, but the rest of SA has a much lower IR. A preponderance of MG starting after the age of 50 years reflects a worldwide trend, although the CT data showed a relatively lower-than-expected incidence for older males. IRs for SPMG vary widely in different regions in SA; this is likely to be related to differences in regional health care delivery, and underdiagnosis.
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    Relationship between environmental exposure to pesticides and anthropometric outcomes of boys in the rural Western Cape, South Africa
    (2013) Ochieng, A A; Dalvie, M A; Little, F; Kromhout, H
    BACKGROUND: Rural residents in the Western Cape (WC), South Africa (SA) are highly exposed to agricultural pesticides that could impact their reproductive development. However, epidemiological evidence of the effect of pesticides on pubertal growth is contradictory. OBJECTIVE: To investigate the effect of pesticide exposure measured using indices of environmental exposure to pesticides on the pubertal growth of boys in rural WC, SA. METHODS: A cross-sectional study of 269 boys (177 of whom gave a history of residing on farms) was conducted. A questionnaire was administered, height and weight were measured and body mass index was calculated. A proximity index (PI) and spraying index (SI) was developed, measuring the lifetime average home distance from pesticide spraying and average frequency of spraying pesticides on a farm, respectively. RESULTS: Median age of boys was 12.4 years (interquartile range 9.5 - 13.3). More than 60% boys had height and weight <50th percentile for age. After adjusting for confounders, PI was significantly associated with shorter stature and lower weight (-1.7 cm/10-fold decrease, p=0.02 and -1.24 kg/10-fold decrease, p=0.04; respectively) and SI was non-significantly associated (-1.4 cm/10-fold increase, p=0.05 and -1.1 cm/10-fold increase, p=0.06; respectively). Associations were stronger for boys aged <11 years and were weaker when excluding non- farm boys. There were no other associations between outcome and exposure. CONCLUSIONS: The use of quantitative exposure indices showed that lower heights and weights might be associated with pesticide exposure in farm boys v. non-farm boys, but not among farm boys. Lower anthropometric measurements among farm boys v. non-farm boys appear stronger at a younger age. The indices of environmental exposure to pesticides require further development.
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    Risk of malignancy in myasthenia gravis patients exposed to azathioprine therapy for a median period of 3 years
    (2006) Rawoot, A; Little, F; Heckman, J
    The long-term risk of malignancies in patients treated with immunosuppressive drugs is a concern among patients and physicians. Patients with myasthenia gravis (MG) respond well to azathioprine (Aza) but many require longterm treatment. The therapeutic effect is presumably largely due to reduced proliferation of actively dividing lymphocytes; however, the benefit of suppressing autoreactive lymphocytes may theoretically result in a concomitant reduction of immunosurveillance and thereby increase the risk of cancer. Many have assessed the malignancy risk in autoimmune diseases such as inflammatory bowel disease (IBD) and rheumatoid arthritis (RA), but these may have their own inherent risk such as colorectal cancer in IBD or lymphoma in RA.1,2 Few studies have been published related specifically to Aza exposure and cancer risk in MG.3,4 This report concerns the incidence of cancer in a South African MG cohort specifically assessing the Aza dose and the duration of treatment.