Clinical manifestations of the twin brothers. a–h. Clinical features and radiographs of the proband. i–m. Clinical features of the proband and his twin brother (left, the proband; right, his twin brother). a, i. Thickening and furrowing of the facial skin. b c, j, and k. Digital clubbing of the fingers and toes. d, l, and m. Swelling of the knees and ankles. e–h. Radiographs of the hands, knees, and feet.