The Marshall and Stickler syndromes: objective rejection of lumping.

To answer the question of whether nosological splitting of the Marshall and Stickler syndromes is justified at the phenotypic level, we surveyed published reports on the two syndromes and applied an objective method to determine this. A set of 18 patients with clinical description, photographs, and radiographs was used to tabulate a list of 53 signs. Cluster analysis using these signs showed that there are two groups of patients with different phenotypes. An index score based on the 20 most discriminating signs was applied to other reported patients and the authors' diagnosis confirmed. There is therefore no objective reason to consider that these two syndromes are not separate dominant disorders with variable expressivity.