Epidemiologia de los nevos pigmentados congenitos: III - Heredabilidad. / Epidemiology of congenital pigmented nevus: III - Heredity

La frecuencia de nevos pigmentados congenitos (NPC) en una serie de nacimientos consecutivos, entre los anos 1967 y 1979, fue 283/30.091 = 0,94%, sin existir diferencias por sexo. Esta frecuencia registrada esta viciada por subregistro, estimandose que la frecuencia real de los NPC debe estar entre 1,5 y 2,0%. Este subregistro afecta principalmente a los NPC leves (unicos, menores de 10 mm, de textura normal), por lo que la proporcion de nevos "graves" debe ser interpretado de acuerdo a la tasa global de incidencia esta 12 veces mayor que la de la poblacion en general. Esta agregacion familiar parece deberse a un mecanismo de herencia multifactorial de alta heredabilidad (H2 = 83,5%), sin indicacion de efectos de dominancia

Epidemiologia de los nevos pigmentados congenitos: III - Heredabilidad. / Epidemiology of congenital pigmented nevus: III - Heredity

La frecuencia de nevos pigmentados congenitos (NPC) en una serie de nacimientos consecutivos, entre los anos 1967 y 1979, fue 283/30.091 = 0,94%, sin existir diferencias por sexo. Esta frecuencia registrada esta viciada por subregistro, estimandose que la frecuencia real de los NPC debe estar entre 1,5 y 2,0%. Este subregistro afecta principalmente a los NPC leves (unicos, menores de 10 mm, de textura normal), por lo que la proporcion de nevos "graves" debe ser interpretado de acuerdo a la tasa global de incidencia esta 12 veces mayor que la de la poblacion en general. Esta agregacion familiar parece deberse a un mecanismo de herencia multifactorial de alta heredabilidad (H2 = 83,5%), sin indicacion de efectos de dominancia

Epidemiology of congenital pigmented naevi: II. Risk factors.

Genetic and environmental risks factors were investigated in a sample of 989 non-malformed newborn infants with skin pigmented naevi (PN), and in 989 non-malformed non-PN, control babies. The samples were obtained from a population of 531,831 livebirths, from fifty-nine South-American maternity hospitals. No significant differences were observed between the PN and control groups for the following risk factors: sex, twinning, parental consanguinity, socioeconomic level, parental ages, birth order, fetal presentation, type of delivery, postnatal mortality, and first trimester of pregnancy histories for maternal chronic illnesses or immunizations, radiation exposure, drug intake, and vaginal bleeding. PN infants were associated with high frequencies of Black racial ancestry, positive prenatal history for maternal acute illnesses, and high mean values for length of gestation and birth weight. The observed association of PN with maternal acute illnesses could be a spurious one, due to partial dependence upon Black racial ancestry, and to maternal memory bias. The analysis of the intrauterine growth curves showed that PN infants have a low prematurity rate, and a high mean by the control newborn group. This observation suggest that congenital PN appear in the latest stages of intrauterine development. No evidence was obtained to allow us to consider congenital PN as true developmental anomalies.

Syndactyly: frequency of specific types.

Syndactyly without other combined limb anomalies, Poland complex, or amniotic bands, was diagnosed in 174 of 599, 109 consecutive newborn infants (3/10,000). Syndactyly was the only diagnosed anomaly in 133 cases, and it was associated with other anomalies in 41. The most common type of syndactyly was isolated syndactyly of the second and third toes (70 cases), which affected more males than females, and had a higher than expected frequency of white non-Latin-European ancestry. The second most frequent type was isolated syndactyly of the middle and ring fingers (18 cases), and the third was isolated syndactyly of the fourth and fifth toes (13 cases). Considering both isolated and syndromal cases, 66% (114/172) could be assigned to one or another of the fourth genetic categories of syndactyly described by Temtamy and McKusick [1978]. This, plus the high frequency of affected first degree relatives observed (25/434:6%), suggests that the genetic forms of syndactyly may be more common than might be suspected from the small number of pedigrees in the literature.