Achondroplasia and sleep-disordered breathing

Rising mercury after receipt of thimerosalcontaining vaccines —Sarah S. Long, MD

Respiratory distress in congenital hypothyroidism —Robert W. Wilmott, MD

Achondroplasia and sleep-disordered breathing —Albert M. Li, MB

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his study by Pichichero et al, a United States-Argentina collaboration, completes the assessment of the full range of ethyl mercury (from thimerosal contained in vaccines) elimination kinetics in preterm infants who received a birth dose of hepatitis B vaccine (the current study), through receipt of multiple thimerosal-containing vaccines in infants through 6 months of age (prior studies). The rapid blood half life of ethyl mercury compared with that of methyl mercury in all studies suggests that risk assessment regarding exposure to thimerosal used as a preservative in vaccines should not be based on that of methyl mercury as consumed in food. Article page 495<

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n this issue of The Journal, Shenoy et al report a full-term infant boy who developed respiratory distress on the second day of life and was found to have hypothyroidism from athyreosis. He responded well to treatment with thyroid hormone. The TITF1 gene was sequenced in both the infant and his parents but no abnormalities were found. This is the first description of respiratory distress from pulmonary interstitial disease secondary to congenital hypothyroidism. Article page 593<

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n this issue of The Journal, Ednick et al report an interesting retrospective study that compared polysomnographic features and brainstem MRI in 12 infants with achondroplasia and 12 age-matched controls. The infants with achondroplasia had reduced arousals during sleep and increased propensity to display sleep-disordered breathing patterns in the absence of parentally reported symptoms. The patients also had a smaller foramen magnum when compared with a different set of controls, but there was no correlation between foramen magnum size and respiratory events during sleep. The authors speculate that infants with achondroplasia have an attenuated arousal response that may place them at risk for sudden unexpected death. Article page 510<

Arousal Index Control

Achondroplasia

Arousal Index (/hr)

50 40

p < 0.0001

p = 0.0026

30

p < 0.0001

20 10 0 Total Sleep

Active Sleep

Spontaneous Arousal Index Achondroplasia 25

Quiet Sleep

Respiratory Arousal

Control

Achondroplasia

Control

40

20 30

p < 0.0001

p < 0.0001

15 20

10

10

5

0

0

Total Sleep

October 2009

Total Sleep

A3