The primary objective of this study is to determine any causative or associated factors for the development of Nephrogenic Systemic Fibrosis (NSF), Nephrogenic Fibrosing Dermopathy (NFD), or related diagnosis. Our primary focus will be on the previous administration of gadolinium to these patients, but we will also look at other postulated causes and risk factors.

The secondary objective of this study is to assess tissue gadolinium (Gd) levels in five groups of subjects:

• Those affected by NSF.
• Those with normal kidney function who have undergone a medical imaging procedure using Gd-based contrast agent (GBCA) in the 2 years prior to a skin biopsy.
• Those with normal kidney function who have never been exposed to GBCA and have had a skin biopsy.
• Those on dialysis or with eGFR ≤ 30 ml/min/1.73 m2 who have had a medical imaging procedure using GBCA in the 2 years prior to skin biopsy.
• Those on dialysis or with eGFR ≤ 30 ml/min/1.73 m2 who have never been exposed to GBCA and have had skin biopsy.

We hypothesize that there is a correlation between the administration of Gd-containing agents usually associated with MRI procedures and the development of NSF in those with renal failure and some other predisposing condition. We also hypothesize that tissue Gd levels in those with NSF will be higher than in those who have been exposed to GBCA but do not have NSF. Of the two groups without NSF but with exposure to GBCA, we hypothesize that those with kidney dysfunction will have higher tissue Gd levels than those with normal kidney function. We hypothesize that in the two groups of subjects without exposure to GBCA, there will be no detectable levels of Gd, regardless of kidney function status.

NSF group

Inclusion Criteria:

• Biopsy-confirmed diagnosis of NSF

Exclusion Criteria:

• Does not have NSF

Normal renal plus gadolinium exposure

Inclusion Criteria:

• eGFR >30
• Existing skin tissue sample
• Gadolinium exposure in 2 years preceding skin biopsy

Exclusion Criteria:

• Does not fit inclusion criteria

Abnormal renal plus gadolinium exposure

Inclusion Criteria:

• eGFR <30 or on dialysis
• Existing skin tissue sample
• Gadolinium exposure in 2 years preceding skin biopsy

Exclusion Criteria:

• Does not fit inclusion criteria

Abnormal renal without gadolinium exposure

Inclusion Criteria:

• eGFR <30 or on dialysis
• Existing skin tissue sample
• No gadolinium exposure ever

Exclusion Criteria:

• Does not fit inclusion criteria

Normal renal without gadolinium exposure

Inclusion Criteria:

• eGFR >30
• Existing skin tissue sample
• No gadolinium exposure ever

Exclusion Criteria:

• Does not fit inclusion criteria

Controls (neonatal)

Inclusion Criteria:

• Existing skin biopsy tissue that was performed within the first 6 months of life

Exclusion criteria:

• Does not fit inclusion criteria

Those with NSF (25). 40 subjects selected through Northwestern University Department of Dermatology's existing medical records and pathology specimens. Medical records will be reviewed to identify 10 subjects who have had a standard of care skin biopsy in the dermatology clinics at Northwestern University and who were exposed to Gadolinium in the 2 years prior to skin biopsy. Another 10 subjects who have had skin biopsy and who have never been exposed to GBCA during a medical imaging procedure will also be identified. Another 10 subjects on dialysis or with eGFR ≤30 exposed to GBCA in the 2 years prior to skin biopsy will be identified. Another group of 10 subjects on dialysis or with eGFR ≤30 who have had skin biopsy and who have never been exposed to GBCA during a medical imaging procedure will also be identified. Neonatal skin tissue of up to 10 subjects with existing skin tissue sample will be sent for analysis.