From the Guidelines
Fat necrosis in neonates is primarily caused by trauma during delivery, particularly in large babies or difficult births involving forceps or vacuum extraction, as well as hypothermia and other perinatal factors. This condition occurs when subcutaneous fat becomes damaged, leading to inflammation and hardening of fatty tissue, typically appearing as firm, well-defined nodules under the skin. Other contributing factors include:
- Maternal conditions such as gestational diabetes or preeclampsia, which can affect fetal growth and development
- Hypoxic events during birth that reduce oxygen supply to tissues, triggering fat necrosis
- Cold stress, which can lead to poor perfusion and subsequent damage to fat cells, as seen in cases of scrotal fat necrosis where recent cold exposure is a common factor 1 The condition is generally self-limiting and resolves within weeks to months without specific treatment, though monitoring for rare complications like hypercalcemia is recommended. Reassurance to parents is important, as these lesions typically heal completely without scarring or long-term consequences. It's essential to note that while the study on scrotal fat necrosis 1 provides insight into the effects of cold exposure, the primary cause of fat necrosis in neonates remains related to perinatal trauma and hypothermia.
From the Research
Causes of Fat Necrosis in Neonates
- Fat necrosis in neonates, also known as subcutaneous fat necrosis of the newborn (SCFN), is a rare disease that occurs in the first days of life 2.
- Several risk factors have been identified, including:
- Maternal factors: gestational diabetes, hypertensive diseases during pregnancy 2, high blood pressure 3, and diabetes 3.
- Birth characteristics: macrosomia (> 4000g) 2, asphyxia 2, 4, therapeutic hypothermia 2, 4, cord prolapse 4, meconium aspiration 4, and sepsis 4.
- Newborn factors: failure to thrive 3, cardiac surgery 3, and exposure to active or passive smoking during pregnancy 3.
- Other potential risk factors include familial or newborn risk factors for thrombosis 3, dyslipidaemia 3, and forceps delivery 3.
Pathophysiology and Clinical Manifestations
- The pathophysiological mechanisms causing SCFN are not fully understood yet 2.
- SCFN is characterized by hard nodules in subcutaneous tissue, purple or erythematous in color, which appear on the upper back, cheeks, buttocks, and limbs 2.
- The disease is often self-limiting, with nodules disappearing in up to 6 months 2.
- Hypercalcaemia is a severe complication associated with SCFN, which can lead to lethargy, hypotonia, irritability, vomiting, polyuria, polydipsia, constipation, and dehydration 2, 4.
Diagnosis and Imaging
- The diagnosis of SCFN is based on the child's history and physical examination, but imaging can be helpful when in doubt 5.
- Ultrasound (US) is the imaging modality of choice to confirm the diagnosis of SCFN, as it provides the best resolution of superficial lesions, requires no sedation, and lacks ionizing radiation 5.