Absence of the proximal phalanx of the thumb. In contrast to the proximal phalanges of the digits 2-5, the proximal phalanx of the thumb is embryologically equivalent to the middle phalanges of the other digits, whereas the first metacarpal is embryologically of phalangeal origin and as such equivalent to the proximal phalanges of the other digits.
Aplasia of the 1st metacarpal
Aplasia of the distal phalanx of the thumb
Short proximal phalanx of thumb
Synonyms
Exact Synonyms:
Absent innermost thumb bone
;
Absent ossification/absent proximal thumb phalanx
;
Aplasia of the proximal phalanx of the thumb