Familial scleroderma: nature, nurture or both?

The aim of the study was to investigate: (i) familial scleroderma (FS) risk factors, (ii) subtype concordance and (iii) relationship between dates (DSO) and ages (ASO) at scleroderma onset.

Forty-seven cases (23 families; 25 FS pairs) were identified. Scleroderma disease onset was defined by (i) Raynaud's onset, (ii) first symptom onset (1SxO), (iii) second symptom onset (2SxO) and (iv) scleroderma diagnosis (SDx).

Female : male and limited : diffuse (L : D) ratios were 8.4:1 and 3.3:1. The Raynaud's onset - SDx interval was longer in limited disease (L : D = 14.6:3.1 years; P = 0.01). Raynaud's first occurred in 36% women > or =50 years. The median differences in ASO between affected family members were 10-12 years. Disease subtype concordance exceeded discordance (16:9 clusters; (P = 0.32) 16:7 families; (P = 0.17)). The observed/expected LL : LD : DD ratios were 14: 8:1/11:7:1 (P = 0.66). FS affected 34% (95% confidence interval 19-50) sister-sister and 44% (95% confidence interval 27-75) mother-daughter pairs. The second family member's SDx was made at the same (9%) or a younger age (80%) than the first family member. In 14 LL disease families ASO was closer between sisters than mothers-daughters (P = 0.07). There was a trend towards closer ages - than dates - at Raynaud's and 1SxO in scleroderma-affected family members (P = 0.054) and closer dates - than ages - at 2SxO (P = 0.02) and SDx.

FS showed female predominance, relatively late onset Raynaud's, subtype ratios similar to idiopathic scleroderma and earlier SDx in younger family members. Familial L scleroderma has a longer prediagnostic latency than familial D scleroderma. FS is likely under-ascertained. In LL scleroderma, Raynaud's/1SxO is possibly more genetically determined and 2SxO/SDx more environmentally determined.