Broad thumbs and/or broad halluces
Page most recently updated 7 September 2026
This page focuses on broad thumbs and/or broad halluces as a morphologic feature of conditions that may also be associated with psychiatric manifestations, such as psychosis, mania, autism spectrum disorder, ADHD, OCD, and self-injurious behaviours. The page begins with a clinical definition of broad thumbs and/or broad halluces based on the standardized Elements of Morphology terminology, together with visual examples from the same source. This is followed by a list of conditions in which broad thumbs and/or broad halluces have been described in association with psychiatric manifestations.
Of note, to optimize clinical utility, the list does not include conditions associated with intellectual disability in the absence of other psychiatric features.
Each condition listed below is linked to a dedicated page within this resource. These pages describe the psychiatric manifestations associated with each condition, as well as other morphologic and broader clinical features, allowing the differential diagnosis to be considered from multiple perspectives.
Broad thumbs
Image credit: National Human Genome Research Institute (NHGRI), Elements of Morphology.
Broad hallux
Image credit: National Human Genome Research Institute (NHGRI), Elements of Morphology.
Definition
Subjective:
Broad Thumb: Increased thumb width without increased dorso-ventral dimension.
Broad Hallux: Visible increase in width of the hallux without an increase in the dorso-ventral dimension.
Note: There is substantial variability in thumb width and it may be difficult to determine the threshold for this finding. As it is commonly bilateral, comparing to the contralateral thumb will not be helpful. This term should not be used for thumbs that meet the definition for Macrodactyly. The assessment is difficult when the thumb is short.
Girth may be increased in a broad hallux, but this must be distinguished from Macrodactyly because there the length is also increased. This assessment may be difficult when the hallux is short.
Conditions with potential psychiatric associations
Selected references and further reading — Morphologic lens
Allanson JE, Biesecker LG, Carey JC, Hennekam RCM. Elements of morphology: introduction. Am J Med Genet A. 2009;149A(1):2-5.
Hennekam RCM, Biesecker LG, Allanson JE, Hall JG, Opitz JM, Temple IK, Carey JC; Elements of Morphology Consortium. Elements of morphology: general terms for congenital anomalies. Am J Med Genet A. 2013;161A(11):2726-2733.
Jones KL, Jones MC, del Campo M. Smith's recognizable patterns of human malformation. 8th ed. Philadelphia: Elsevier; 2021.
Reardon W. The bedside dysmorphologist: a guide to identifying and assessing congenital malformations. 2nd ed. Oxford: Oxford University Press; 2016.