The clinical genetics of hidradenitis suppurativa revisited.

A familial form of hidradenitis suppurativa (HS) with autosomal dominant inheritance was described in a study conducted 15 years ago in Nottingham but has not been systematically confirmed elsewhere. Prior to commencing molecular genetic studies, we wanted to test the validity of the previous study by assessing its reproducibility on the basis of a strict, newly devised disease definition for HS. We were also interested whether new cases of the disease had arisen meantime in the study group as should be expected for an autosomal dominant disease. We reviewed 14 surviving probands and their families. Seven of these probands had previously been noted to have a positive family history whereas the others had been classified as having a negative or possible family history. One hundred and thirty-two family members were assessed for their respective disease status. Participants were initially contacted by telephone or letter, and those who acknowledged a history of at least one previous boil were invited for a personal examination and interview. Only personally examined individuals were classified as a case. Twenty-eight relatives with HS were detected in total, and 27 of these were in the group previously labelled family history positive. Nine of these cases had not been detected in the previous study and in at least seven of these the disease had developed after the previous study had been conducted. Only twice did our criteria fail to confirm cases that had been labelled as HS in the previous study. Both times we classified the patients as 'possibly affected'. A further 16 relatives were judged to be possibly affected. In the group with positive family history we found 10 affected and nine possibly affected individuals among 37 surviving first-degree relatives of HS sufferers. Our findings support the concept of a familial form of HS with autosomal dominant inheritance. An insufficiently sensitive disease definition, a variable degree of gene penetrance and possibly a hormonal influence on gene expression may explain the reduced risk to first-degree relatives, which falls short of the expected 50% mark. Molecular genetic studies to clarify whether one or more gene(s) are involved in HS are now necessary and have been commenced.