Spinal muscular atrophy is a common autosomal recessive neuromuscular disorder caused by the homozygous loss of the SMN1 gene. The absence of the SMN1 gene has been shown to occur in all types of SMA, childhood and adult forms. In rare cases, asymptomatic family members have also been found with homozygous mutations in the SMN1 gene, suggesting a role for phenotypic modifiers. We describe three unrelated asymptomatic individuals, with family histories of SMA, who were shown to have the homozygous SMN1 deletion. Quantitative studies indicated that the three individuals all had increased SMN2 copy numbers. These cases not only support the role of SMN2 in modifying the phenotype, but our data also demonstrate that expression levels consistent with five copies of the SMN2 genes maybe enough to compensate for the absence of the SMN1 gene. Lastly, in cases similar to the ones described, the measurement of the SMN2 gene copy number may provide valuable prognostic information.

No abstract

An epidemiologic investigation of an acupuncturist's practice in Rhode Island identified 35 patients who were infected with hepatitis B virus during 1984. Of 366 patients seen by the acupuncturist during 1984, 316 (86%) completed questionnaires and submitted serum for hepatitis B serology. Use of tests for immunoglobulin M antibody to hepatitis B core antigen (IgM anti-HBc) identified 17 case-patients who otherwise may have gone undetected. Thirty-four of the 35 case-patients were treated in only one of the two clinics run by the acupuncturist. Patients who received a greater number of acupuncture needles during their treatment course were more likely to have been infected; the attack rate for patients who received less than 150 needles was 9%, compared with 33% for patients who received greater than or equal to 450 needles (p less than 0.001). Attack rates were higher during a one-month period when the index case-patient was more likely to have been viremic than during any other period in 1984 (relative risk = 4.1, 95% confidence interval = 2.3-7.3). While observing the acupuncturist's technique, the investigators noted several potential mechanisms for needle contamination. This study highlights the potential for transmission of hepatitis B in situations of repeated needle use.