Coancestry in apparently sporadic primary pulmonary hypertension.

OBJECTIVE To examine sporadic cases of primary pulmonary hypertension of coancestry. DESIGN An epidemiologic study of families of patients with primary pulmonary hypertension. SETTING A university-affiliated referral population. PARTICIPANTS Family members of 13 patients with primary pulmonary hypertension. MEASUREMENTS Family pedigrees involving grandparents, parents, siblings, and children were supplemented by genealogic records. Coefficients of kinship (Ck) were calculated for the patients with primary pulmonary hypertension who demonstrated coancestry and compared with 500 sets of controls drawn at random from genealogic records. RESULTS Two patients with sporadic primary pulmonary hypertension demonstrated coancestry. The great-great grandfather and great-great grandmother of one patient were the great-grandfather and great-grandmother of the other patient. No other cases of primary pulmonary hypertension were identified in these two families. The CK of the affected individuals (CK = 10.02 x 10(-5)) suggests strongly that the observed relationship did not occur by chance alone. Among 500 random sets of matched controls, only two sets yielded CK of 10.02 x 10(-5) or greater (p = 0.004). Coancestry could not be identified for the other five families of patients with sporadic primary pulmonary hypertension for whom genealogic records were available. CONCLUSIONS The finding of coancestry in patients with sporadic primary pulmonary hypertension suggests that a genetic basis exists for some patients with apparently sporadic primary pulmonary hypertension. Familial primary pulmonary hypertension may be more common than previously recognized.