Poland syndrome is a rare congenital condition characterized by the underdevelopment or absence of muscles on one side of the body, most notably the pectoralis major muscle. This birth defect affects approximately one in 20,000 to 100,000 newborns and typically presents unilaterally, occurring on only one side of the body. The name honors a historical figure who first described the anomaly, rather than implying a geographic origin.
The Historical Context of the Naming
The syndrome is named after Sir Alfred Poland, a British surgeon who first documented the condition in a detailed anatomical report. This initial description was published in the Guy’s Hospital Reports in 1841 while Poland was still a medical student conducting a dissection. His paper, titled “Deficiency of the pectoral muscles,” outlined the findings in the body of a deceased convict.
Poland’s original observation focused on the absence of the sternocostal portion of the pectoralis major muscle and the entire pectoralis minor muscle. He also noted related anomalies, including an underdeveloped serratus anterior muscle and small thoracic vessels on the affected side. Alfred Poland himself did not name a syndrome; he simply reported a distinct anatomical finding.
The term “Poland’s syndactyly” was introduced in 1962 by Patrick Clarkson, a plastic and hand surgeon in London. Clarkson noticed a pattern of chest wall defects combined with hand deformities in his patients. He rediscovered Poland’s 1841 report and honored the original observer by attaching his name to the constellation of symptoms, which was later formalized as Poland syndrome.
Primary Clinical Manifestations
The primary feature of Poland syndrome is the partial or complete absence of the pectoralis major muscle on one side of the body. The sternocostal head of the muscle is most commonly affected, often creating a visible flattening or concavity of the chest wall.
Associated features frequently affect the ipsilateral (same side) upper extremity. These often include hand abnormalities such as brachydactyly (shortening of the fingers) and syndactyly (webbing or fusion of the fingers). The forearm may also be shortened due to hypoplasia of the underlying bones.
Other manifestations include hypoplasia of the breast and nipple in females, which becomes more apparent during puberty. Rib cage anomalies are also observed, sometimes involving the absence or underdevelopment of the second through fifth ribs. These skeletal defects can occasionally lead to paradoxical respiratory movements in severe cases.
Proposed Pathogenesis
The most widely accepted explanation for Poland syndrome is the vascular disruption theory, often termed the subclavian artery supply disruption sequence (SASDS). This theory proposes that the condition results from a temporary interruption or reduction of blood flow in the embryonic subclavian artery or its branches. This vascular insult is hypothesized to occur early in development, specifically around the sixth week of gestation.
The subclavian artery system supplies blood to the developing chest wall and upper limb bud. A localized reduction in blood supply leads to hypoplasia, or failure of development, of the muscles and bones. The specific pattern of defects, extending from the chest to the hand, is determined by the exact location and extent of the vascular compromise within the arterial tree.
If the disruption occurs in the internal thoracic artery branch, it primarily affects the pectoral muscles. A more distal interruption can cause the associated limb defects. This model also explains why the condition is almost always unilateral, as the insult affects only the developing vessels on one side of the embryo.
Diagnosis and Therapeutic Approaches
Diagnosis is typically initiated by a physical examination at birth or during early childhood, especially when characteristic unilateral chest wall and hand anomalies are present. Milder forms may go undiagnosed until adolescence when differences in breast development or muscular asymmetry become pronounced. Imaging techniques are utilized to confirm the extent of the anomalies and aid in surgical planning.
Chest X-rays can reveal rib cage abnormalities, while computed tomography (CT) scans offer detailed views of the bone and muscle structure. Ultrasound and magnetic resonance imaging (MRI) are also employed to assess soft tissues, including the pectoralis muscles and the mammary gland. These studies are important before intervention to identify the specific missing or underdeveloped structures.
Management is individualized, focusing on maximizing function and improving aesthetic symmetry. Hand deformities, such as syndactyly, are often addressed surgically in childhood to improve dexterity. For chest wall reconstruction, surgical options include custom silicone implants for males, or tissue expanders, muscle flaps, and breast implants for female patients. Physical therapy supports recovery and helps maintain range of motion.