Table 1 Syndromes associated with hypoplastic thumb

Holt-Oram Syndrome [15]

- Autosomal dominant inheritance.

- Skeletal abnormalities of upper limbs.

- Congenital heart defects.

- Radial ray anomalies, including hypoplastic thumbs.

- Often involves thumb underdevelopment or absence.

Fanconi Anemia [15]

- Bone marrow failure.

- Physical abnormalities

- Increased cancer risk.

- Radial defects, including hypoplastic or absent thumbs.

- May present with bilateral thumb hypoplasia.

VACTERL Association [15]

- Non-genetic association of defects:

Vertebral, Anal, Cardiac, Tracheoesophageal, Renal, and Limb anomalies.

- Limb abnormalities often involve radial hypoplasia or hypoplastic thumbs.

- Thumb anomalies are part of the limb defect spectrum.

TAR Syndrome [15]

- Autosomal recessive inheritance.

- Thrombocytopenia (low platelets).

- Bilateral absence of the radius.

- Thumb is usually present but may be hypoplastic.

- Radial defects can affect thumb development indirectly.