Brachydactyly A1 is characterized by shortening or absence of the middle phalanges of all digits. The second and fifth digits are most severely affected. A variety of skeletal findings with brachydactyly have been reported, but in general, this disorder has not been well defined. We present 2 families with brachydactyly A1 and other skeletal abnormalities not previously described. The proband in the first family is a 40-year-old male. His history was significant for short hands and feet in addition to club foot and elbow surgery to remove cartilage. Although he is of normal stature, his arm span/height ratio was decreased and his upper/lower segment ratio was increased, suggesting short limbs. He was noted to have limited dorsiflexion of his ankles and wrists. Skeletal survey showed bilateral shortening of the middle phalanges in the upper extremities with accessory ossicles, scoliosis, spurring and lateral flaring of the iliac wings bilaterally, abnormal tufting of distal phalanges of feet with appearance of absence of mid or proximal phalanges and tarsal fusion. Family history is significant for similar hand findings in multiple family members consistent with autosomal dominant inheritance. The proband in the second family is a 4-year-old girl referred to our clinic for short stature. On exam she was noted to have hallux valgus and syndactyly of her second and third toes. Her skeletal survey revealed marked shortening of the middle phalanges of the second, third, and fourth fingers bilaterally; abnormal overgrowth of the proximal epiphyses of the proximal second and third phalanges bilaterally; and normal long bones and vertebrae. Her mother is also affected with brachydactyly of her hands with syndactyly of her toes and microcephaly. Her films showed symphalangism, a narrow 4th metacarpal, narrowing and irregularity of the IP joint of the thumb and DIP joints, short middle phalanges of the 5th fingers bilaterally, absent middle phalanges over the 4th and 5th toes with fused DIP joints, and shortened 3rd and 4th toes bilaterally. The widely variable findings in these two families suggest that brachydactyly A1 is not a single disorder and that careful clinical and radiographic evaluations are necessary to further delineate the subgroups. Brachydactyly A1 is typically considered to be an isolated finding but can be a heterogeneous disorder with more generalized skeletal manifestations. Better genotype-phenotype correlation is needed. Mutations responsible for brachydactyly A1 have been described involving the Indian hedgehog gene. Testing for our patients is pending at this time. It is possible that different genes may be responsible for the variable phenotypes.
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