A clinical characterization of familial keloid disease in unique African tribes reveals distinct keloid phenotypes.

BACKGROUND This study is a clinical characterization of keloid scars in an African population comprising three rural tribes with familial keloids. Site distribution, morphologic features, and other characteristics of the scars were studied to assess whether each tribe had a specific scar phenotype. METHODS Keloid scar clinics were set up at Soba Hospital in Khartoum, Sudan, for patient recruitment and management. In addition, familial keloid cases were recruited from rural tribal populations during field trips. A database including clinical and demographic data and digital photographs of all keloid cases was established. Statistical analysis was conducted using SPSS and SAS software. RESULTS One hundred eleven individuals with keloid scarring (67 male subjects and 44 female subjects) were recruited. Patients were predominantly from three multigenerational pedigrees (total of 38 nuclear families) afflicted with keloid scars residing in different rural regions of Sudan. Two distinct morphologic phenotypes of keloid scarring were observed. The first phenotype has been designated "superficial spreading" (horizontal) keloid and the second has been designated "raised" (vertical) keloid. Clinically significant features and statistically measurable morphologic parameters were compared among these phenotypes (p = 0.001). Furthermore, linear claw-like extensions of keloid (transgression) were noted to be significantly higher in the superficial spreading keloid phenotype (p = 0.03). CONCLUSIONS There is strong evidence of different phenotypes of keloid scarring. Two distinct phenotypes have been observed, described, and statistically verified. Each tribe demonstrated one particular phenotype, with two being superficial spreading and one being raised. Other significant clinical characteristics have been described. This is of significance in understanding both the clinical basis and the genetic basis of keloid scarring.