Table 2.

Hidradenitis suppurativa and associated diseases

Disease			Gene map loci	Dysregulated genes	Encoding protein	Reported cases associated with HS	References
Inflammatory bowel diseases
(1) Crohn disease (CD), ulcerative colitis					caspase recruitment	82	47–74
			16q12	NoD2/CARD15	domain-containing	81	48–63
(2) Crohn disease (CD) and squamous cell carcinoma (SCC)					protein	1	74
SAPHO (synovitis, acne, palmoplantar pustulosis, hyperosteosis, osteitis) syndrome						9	75–77
Pyoderma gangrenosum						7	78, 79
Adamantiades-Behçet disease (ABD)				HLA-B51, IL -12B	promoter of IL-12	5	80–84
Spondylarthropathy SPDA1
		SPDA2		HLA-B27		59	85–95
			6p21.3		endoplasmic reticulum aminopeptidase 1
(1) without additional signs			9q31–q34	IL-1, IL-23, ERAP1, TNFSF15, HLA negative	tumor necrosis factor superfamily, member 15	37	86–90
(2) with acne conglobata only or follicular occlusion triad (HS, acne conglobata, dissecting cellulites of the scalp)						22	86, 91–95
Genetic keratin disorders associated with follicular occlusion						42	96–107
(1) Pachyonychia congenita (pC-2)						26	96–99
(2) Dowling-Degos disease			17q12-q21	KRT 17	cytokeratin-17	16	100–107
	(a) without additional signs		12q13	KRT6B	cytokeratin-6B	12	100–104
	(b) with arthritis		12q13	KRT5	cytokeratin-5	2	105
	(c) with squamous cell carcinoma (SCC)					2	106, 107
Other genetic disorders (1) Keratitis-ichthyosis-deafness (KID) syndrome			13q11-q12	GJB2	GAP junction protein beta-2 = connexin-26	4	45, 108–110
(2) Down's syndrome			1q43, Xp11.23, 21q22.3	e.g., GATA1	globolin transcription factor 1	3	111
Epithelial tumors*						38	112–118
(1) squamous cell carcinoma (SCC)*			7p11.2 11q13.3	ECOP CCND1	EGFR (epidermal growth factor receptor)-co-amplified and overexpressed protein	37	112–117
(2) adenocarcinoma*					cyclin D1	1	118

^*SCC and adenocarcinoma have to be considered as a consequence of chronic inflammation and not as a real comorbidity