Triangular Facies

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Triangular facies describes a face shape that is wide at the temples and narrows to a small chin, often with a pointed chin tip. This gives a triangle or inverted triangle appearance. It is sometimes accompanied by a prominent forehead and down-turned corners of the mouth. Triangular facies can be seen in certain growth disorders and bone disorders.

Associated Conditions

Osteogenesis Imperfecta (OI)

Also known as brittle bone disease, most forms of OI (especially Type III and some Type IV) manifest a characteristic triangular facial shape.

Facial: Infants and children with moderate-to-severe OI often have a broad forehead (sometimes with frontal bossing), relative proptosis (eyes appearing prominent due to shallow orbits), and a small pointed chin – collectively described as triangular facies​. There may also be blue sclerae (bluish hue of the whites of the eyes due to thin collagen) and dentinogenesis imperfecta (opalescent teeth), but those are ocular and dental findings, respectively.

MSK: OI is a collagen type I disorder leading to fragile bones that fracture easily. Multiple fractures can occur with minimal trauma, leading to bone pain, deformities (limb bowing, scoliosis), and early arthritis in weight-bearing joints. Type III OI, for instance, presents in infancy with fractures and can result in short stature, spinal curvature, and basilar invagination (upward protrusion of the upper spine into the skull) which can cause neck pain and neurological issues​.

Relevance: The triangular facies in an infant with fractures might suggest OI, which has immediate implications for handling (gentle positioning to avoid fractures) and later orthopedic management (rodding of long bones, bisphosphonate therapy to strengthen bone). From a pain perspective, these patients experience acute pain from fractures and chronic pain from deformities. Recognizing the syndrome allows for proper pain management strategies (e.g. intramedullary rods to stabilize bones and reduce recurrent fracture pain, physiotherapy, caution with surgical procedures due to bone fragility). Also, knowing it’s OI (versus child abuse, which can be an initial concern in infants with fractures) changes the entire approach—OI is treated medically and supportively, not punitively. Diagnostic: Genetic testing of COL1A1/COL1A2 or a collagen biochemical analysis confirms OI. The facial features plus the presence of blue sclerae and multiple fractures typically clinch the diagnosis in childhood.

Russell-Silver Syndrome (RSS)

A primordial growth retardation syndrome (commonly due to imprinting defects on chromosomes 7 or 11).

Facial: Children with Russell-Silver have a striking triangular face: broad high forehead that protrudes, and a small jaw with down-turned corners of the mouth​. The chin is pointed and small (often there is concomitant micrognathia). The face appears small relative to head size (because head growth is relatively spared in this disorder).

MSK: RSS children are born small-for-gestational-age and remain short; they often have limb length asymmetry (hemihypertrophy on one side). While they don’t have joint disease per se, the leg length discrepancy can cause gait imbalance and, if significant, hip/back pain due to compensatory scoliosis or pelvic tilt. They may also have clinodactyly of the 5th finger and early feeding difficulties.

Relevance: Triangular facies in a toddler who is failing to thrive should prompt consideration of Russell-Silver syndrome. Diagnosing RSS is important for offering growth hormone therapy which can improve final height and possibly muscle mass. Though not classically described as a pain condition, one must monitor for complications of asymmetry – for instance, a child with one leg significantly longer might need orthotic intervention to prevent back pain. Additionally, RSS patients have an increased risk of hypoglycemia in infancy (due to low muscle mass and feeding issues), which can cause irritability and possible neurologic harm (seizures). Recognizing the syndrome helps manage nutrition and metabolic concerns.

Hallermann-Streiff Syndrome

A very rare syndrome characterized by bird-like facies (thin, small beak-shaped nose and micrognathia) and proportionate short stature. These patients have a triangular face with micrognathia, but also distinctive features like micropthalmia (small eyes) and skin atrophy on the nose. Orthopedically, they can have hypotonia and some joint laxity. Not a common cause of pain, but airway issues from micrognathia and glaucoma (eye pain) can occur.

Other contexts

A triangular face can sometimes be observed in untreated congenital hydrocephalus after shunting – the forehead remains prominent while the face doesn’t catch up in growth. Some children with long-term growth hormone deficiency or malnutrition also have relatively large-appearing heads with narrow chins (pseudo-triangular facies). In these cases, addressing the underlying condition (shunt the hydrocephalus, treat the hormonal deficiency) changes the facial growth trajectory.

Why it matters

Triangular facies often indicates a growth or bone maturation issue. In OI, it correlates with severe disease requiring intensive management to reduce fractures (and thus pain). In RSS, it correlates with severe intrauterine growth restriction and the need for hormonal and nutritional support. The presence of triangular facies in a child should prompt evaluation for short stature, asymmetry, or fractures, depending on context. Additionally, triangular facies with micrognathia (as in OI or Hallermann-Streiff) can signal potential airway problems during anesthesia or sleep. For example, an anesthesiologist seeing a triangular-faced patient might anticipate a difficult intubation due to a small jaw (important in OI, which also may have basilar invagination). Pain management in triangular-facies conditions usually revolves around the underlying cause: for OI, fracture care and medications like bisphosphonates to strengthen bone (reducing fracture frequency and pain)​; for RSS, ensuring the child gets adequate caloric intake to avoid headaches or abdominal pain from hypoglycemia.

Diagnostic Note

Triangular facies is observed clinically. In OI, radiologic findings (osteopenia, multiple healing fractures, Wormian bones in skull) plus genetic tests confirm the diagnosis. In RSS, the Netchine-Harbison clinical scoring includes criteria like relative macrocephaly, protruding forehead, and feeding problems​. Genetic tests (methylation analysis of 11p15 and UPD7 testing) confirm about 60% of cases​. Importantly, if triangular facies is noted, one must measure growth parameters and consider differential diagnoses: if the child is short with asymmetry – likely RSS; if normal stature but fractures – likely OI; if normal growth but just facial feature, could be familial or something like Sotos (though Sotos usually has a long face, not small chin). Triangular facies in an adult is less commonly discussed, but could result from long-standing conditions or significant weight loss in the face.