A female infant, first seen at age 7 months and again at 1 3/12 years, exhibited the following physical findings: low birth weight at full term; mental and growth retardation; brachycephaly; micrognathia; high arched palate; low set, slanted malformed pinnae; scant medial eyebrow hair; small, short nose with prominent skin folds over the nasal bridge; short neck; both hands were hypoplastic between thumb and index finger; a tendency to hold thumbs in pronation; abnormal dermatoglyphics; rocker-bottom feet; big toes kept in dorsi-flexed position; mottled skin; hypoplastic clitoris and labia minora.
Cytogenetic studies on the patient revealed that 83% of the karyotyped peripheral leucocytes had 46 chromosomes and 17% had 47 chromosomes. Metaphases with 46 chromosomes exhibited the normal female complement. Metaphases with a count of 47 consistently had an extra chromosome in the C group. A labelled metaphase with 47 chromosomes showed only 1 late-replicating chromosome. The sex chromatin count was positive (30%) and no buccal cells with more than one sex chromatin body were observed.
This study was supported in part by grants T1-AM-5277 and AM-02504 from the National Institutes of Health, United States Public Health Service.
Postdoctoral trainee, National Institute of Arthritis and Metabolic Diseases.