Diffuse partial woolly hair.

We report 4 new cases presenting with the characteristics of a recently described pilar dysplasia entitled 'diffuse partial woolly hair'. Two of our cases were familial (mother and daughter), while the 2 other were sporadic. Scalp hair of all the patients exhibited two hair shaft populations intermingled throughout the scalp. The first hair type was straight, normally pigmented and of normal length, while the second type was wavy and the shafts were hypopigmented, thinner, shorter and easily pluckable. One of our patients presented with a diffuse hair thinning due to a progressive loss of wavy hairs. Under reflected light, both hair populations displayed alternating dark and bright segments. Scanning-electron microscopic analysis of straight and wavy hairs revealed comparable lesions: torsions, angular kinks, weathering as well as grooved segments alternating with the normal ones. These changes were the most severely expressed in the shortest and the waviest hairs. Taken together, the clinical and microscopic characteristics of this pilar dysplasia justify its introduction as a separate entity into the woolly hair group.