Prevalence of tapeto-retinal dystrophies among Danish children.

Age specific prevalence rates are presented based on 110 cases of pigmentary retinopathy (RP) recorded in the Danish child population of a little over one million individuals on January 1, 1988. A steady and steep rise in age specific prevalences of notified RP throughout infancy and childhood was found. The material consisted in 52 non-systemic and 58 systemic cases. 35 of the systemic cases could be nosologically identified, leaving 23 cases unidentified with respect to known diseases or syndromes. Among the genetic types autosomal recessive inheritance was the most common with 60 cases (55%). Parental consanguinity was less frequent than hitherto reported. On the other hand undetected carrier state for X-linked tapeto-retinal dystrophy played a more significant role than expected. A clear excess of males among the simplex cases indicated that some X-linked cases may still be unrecognized. A significant proportion of non-systemic, early infantile RP with an autosomal recessive or simplex mode of inheritance are clinically and electrophysiologically characterised as cone-rod dystrophies.