Thumb involvement in Raynaud's phenomenon as an indicator of underlying connective tissue disease.

OBJECTIVE: To conduct a retrospective study to assess whether the degree of thumb involvement differs between primary Raynaud's phenomenon (PRP) and secondary Raynaud's phenomenon (SRP).

METHODS: Thermography images from all patients attending Salford Royal Hospital and referred for thermography for assessment of RP between 2004 and 2006 were retrospectively reviewed. A distal dorsal difference (DDD) of -1 degrees C or less between the fingertips and dorsum of the hand (fingers cooler) at 23 degrees C was considered clinically relevant. The worse score (the lower score, i.e., the more negative value) from each pair of digits was considered for analysis.

RESULTS: One hundred seventy patients fulfilled the study criteria. DDD at 23 degrees C for the thumbs were significantly higher (digital tips warmer) compared with other digits (p < 0.001) in both PRP and SRP. All digits were significantly warmer in PRP compared to SRP with the exception of the thumbs. The proportion of patients with clinically relevant involvement of thumbs was significantly higher in SRP compared to PRP (p = 0.003) and this difference was more pronounced in the thumbs compared with other digits.

CONCLUSION: Although the median temperature gradient along the thumb was not significantly different between SRP and PRP, the thumb is more likely to be involved in SRP than in PRP. Thumb involvement is one of a number of clinical indicators that should alert the clinician to the possibility of an underlying connective tissue disease/disorder.