Visceral brown fat necrosis in postperinatal mortality

Brown fat necrosis with calcifications in the newborn: Risk factors, radiographic findings, and clinical course

Objective:

To describe the radiographic appearance of subclinical calcified brown fat necrosis and the associated clinical and laboratory findings.

Materials and Methods:

Picture Archiving and Communications Sytem (PACS) was searched using keywords “soft tissue calcification” and “chest.” The clinical record was searched for prior cardiac surgery, bypass, Extracorporeal Membrane Oxygentation (ECMO) and prostaglandin use. Age when calcifications were first detected, location, resolution, and associated laboratory abnormalities were recorded.

Results:

Nine patients were identified. None had skin lesions. All patients had congenital heart disease and had experienced cardiac/respiratory arrest and/or severe hypotension 1–6 weeks before soft tissue calcifications occurred. Calcifications resolved by 9 weeks to 5 months in 3 patients. The remaining were either deceased or lacked follow-up imaging. Renal ultrasound was performed in all but 1 patient. Nephrocalcinosis was only seen in 1 patient.

Conclusion:

Brown fat necrosis is subclinical, diagnosed on plain film, and likely self-limited. It occurs in term and preterm infants who have undergone significant systemic stress and carries a poor prognosis.

Brown fat distribution in the chest wall of infants-normal appearance, distribution and evolution on CT scans of the chest

BACKGROUND

While reviewing chest CT scans of infants, we repeatedly observed hyperdense enhancing tissue in the chest wall that is not well described in radiology literature.

OBJECTIVE

This study was undertaken to describe the imaging features of this tissue in chest walls of infants.

MATERIALS AND METHODS

CT scans of the chest conducted on all infants between April 2008 and October 2009 were retrospectively reviewed. CT studies with any deviation from normal radiation or contrast dose or those with chest wall anatomical distortion were excluded.

RESULTS

One hundred eighty-eight infants were scanned, with 202 MDCTs, of which 180 (89.1%) received contrast agent. Fifty-four of 180 (30%) cases revealed focal areas of hyperdensity in various locations. All positive cases ranged between 2 days and 9 months of age. The areas of distribution of hyperdensity had excellent correlation with known areas of brown fat in the chest wall, known from nuclear medicine studies, and hence we concluded these to represent the same.

CONCLUSION

Brown fat in the chest wall can be seen as enhancing tissue on contrast CT scans done on infants. This is a normal morphological component with the brown fat converting to normal fat. It is important to recognize it in the chest wall of infants to avoid misinterpretation.

Postulated vasoactive neuropeptide autoimmunity in fatigue-related conditions: a brief review and hypothesis

Disorders such as chronic fatigue syndrome (CFS) and gulf war syndrome (GWS) are characterised by prolonged fatigue and a range of debilitating symptoms of pain, intellectual and emotional impairment, chemical sensitivities and immunological dysfunction. Sudden infant death syndrome (SIDS) surprisingly may have certain features in common with these conditions. Post-infection sequelae may be possible contributing factors although ongoing infection is unproven. Immunological aberration may prove to be associated with certain vasoactive neuropeptides (VN) in the context of molecular mimicry, inappropriate immunological memory and autoimmunity. Adenylate cyclase-activating VNs including pituitary adenylate cyclase-activating polypeptide (PACAP), vasoactive intestinal peptide (VIP) and calcitonin gene-related peptide (CGRP) act as hormones, neurotransmitters, neuroregulators, immune modulators and neurotrophic substances. They and their receptors are potentially immunogenic. VNs are widely distributed in the body particularly in the central and peripheral nervous systems and have been identified in the gut, adrenal gland, blood cells, reproductive system, lung, heart and other tissues. They have a vital role in maintaining cardio-respiratory function, thermoregulation, memory, concentration and executive functions such as emotional responses including social cues and appropriate behaviour. They are co-transmitters for a number of neurotransmitters including acetylcholine and gaseous transmitters, are potent immune regulators with primarily anti-inflammatory activity, and have a significant role in protection of the nervous system against toxic assault as well as being important in the maintenance of homeostasis. This paper describes a biologically plausible mechanism for the development of certain fatigue-related syndromes based on loss of immunological tolerance to these VNs or their receptors following infection, other events or de novo resulting in significant pathophysiology possibly mediated via CpG fragments and heat shock (stress) proteins. These conditions extend the public health context of autoimmunity and VN dysregulation and have implications for military medicine where radiological, biological and chemical agents may have a role in pathogenesis. Possible treatment and prevention options are considered.

Resolution of calcific brown fat necrosis associated with prostaglandin therapy for cyanotic congenital heart disease in neonates: report of two cases

Prostaglandin E1 (PGE1) administration for palliation of cyanotic congenital heart disease in neonates has been associated with radiographically visible necrosis of brown fat about the neck and shoulder girdles. However, the natural history of this process has not been described. We present two patients with cyanotic congenital heart disease, treated preoperatively with prostaglandin E2 (PGE2), both of whom developed dramatic calcific brown fat necrosis. This process slowly resolved over time in both patients.

Is sudden infant death syndrome (SIDS) an autoimmune disorder of endogenous vasoactive neuropeptides?

Sudden infant death syndrome (SIDS) remains a perplexing diagnosis with conflicting laboratory investigation and lack of a biologically plausible aetiology. Investigations into the endogenous vasoactive neuropeptides, including pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are revealing the critical role these substances have in homeostasis including thermo- and cardiovascular regulation. For example, studies in PACAP receptor-deficient mice have revealed sudden neonatal death attributed to respiratory control defects, possibly due to mutations in genes encoding components of PACAP signalling pathways. PACAP and VIP belong to the secretin/glucagon superfamily of hormones and function as vasoactive neuropeptides. They act as hormones, neurotransmitters, immune modulators and neurotrophes. They are readily catalysed to small peptide fragments. They and their binding sites are immunogenic and are known to be associated with a range of autoimmune conditions. Vasoactive neuropeptides have a known role in thermoregulation and deficiency states are associated with higher neonatal death rates in rats. PACAP plays a significant role in carbohydrate and lipid metabolism and impairment of functioning has potentially serious consequences. It is postulated PACAP and VIP receptors in brain may become compromised through autoimmune phenomena resulting in cardio-respiratory dysfunction and death. This paper discusses the potential role of certain vasoactive neuropeptides in causing autoimmune responses in susceptible infants predisposing them to SIDS.

Subcutaneous fat necrosis associated with thrombocytosis in an infant following cardiac surgery

Subcutaneous fat necrosis in infancy is characterized by the appearance of subcutaneous nodules beneath a violaceous or erythematous plaque in infants exposed to ischemic stress from a variety of causes. It has been associated with hypercalcemia, hyperlipidemia and thrombocytopenia. This case of subcutaneous fat necrosis occurred 14 days after cardiac surgery in an infant taking enoxaparin who developed a paradoxical thrombocytosis. A potential etiological role for platelet sludging is discussed. Ultrasound images, not previously reported, showed thickened heterogeneous hypodense subcutaneous fat in the nodules and, thus, may be used to differentiate this condition from its surgical differential diagnoses.

Case report: child abuse--necklace calcification--a sign of strangulation

Strangulation has been postulated as one cause of cerebral hypoxia in child abuse. This report describes the finding of necklace calcification in an infant with rib fractures and a metaphyseal fracture and an admission of a shaking injury. The calcification is likely to represent fat necrosis as the result of strangulation.

Role of noradrenergic innervation of brown adipose tissue in thermoregulatory deficits following prenatal alcohol exposure

The development of thermoregulation in newborns is delayed by prenatal alcohol exposure in an animal model of moderate maternal drinking. Newborn mammals generate heat primarily via nonshivering thermogenesis in brown adipose tissue (BAT), which is activated by the sympathetic nervous system. In this study, the effects of prenatal alcohol exposure on the development of the sympathetic innervation of BAT was investigated by assessing the concentration of norepinephrine (NE) in interscapular BAT. Pregnant dams were given either a liquid diet with 35% of the calories derived from alcohol, a liquid diet without alcohol to control for any effects of the liquid diet administration, or ad libitum food and water. Interscapular brown adipose tissue was excised from 5-, 10-, and 20-day-old male and female offspring. At 5 days of age, alcohol-exposed pups had significantly lower NE concentrations than did pups in either control group. However, 20-day-old alcohol-exposed pups had significantly higher NE concentrations than either control group. These results suggest a delay in the development of the sympathetic activation of BAT thermogenesis, followed by a compensatory overactivation. These findings may have important implications for understanding the mechanisms underlying thermoregulatory deficits seen after prenatal alcohol exposure. In addition, these results suggest that maternal alcohol consumption may increase the risk of sudden infant death syndrome, which has been linked to inappropriate BAT thermogenesis.

Case report: soft tissue and perivisceral calcification occurring in an infant: a case of brown fat necrosis

Fat necrosis is a well described cause of widespread subcutaneous calcification occurring in a young infant. In this condition the radiographic demonstration of soft tissue calcification is often dramatic but is clinically irrelevant since the diagnosis is usually evident without recourse to radiology. Visceral fat necrosis and calcification, in the absence of hypercalcaemia, have been reported occasionally in association with subcutaneous fat necrosis. We report a case with calcification largely confined to deep perivisceral sites without clinical signs of subcutaneous fat necrosis.

Brown adipose tissue activity in pyrexial cases of cot death

Brown adipose tissue was investigated in two cases of cot death in which core temperatures were above 40 degrees C on arrival at the mortuary. Evidence was obtained from mitochondrial (8-3H) guanosine diphosphate (GDP) binding and oxygen uptake of active thermogenesis with uncoupled mitochondrial respiration which was recoupled by GDP. Thermogenic capacity of brown adipose tissue, estimated by radioimmunoassay of the specific mitochondrial membrane "uncoupling protein" responsible for heat production, was similar to that measured in other infants or in experimental animals acclimated to moderately warm conditions (23 degrees C). Brown adipose tissue thermogenesis, occurring inappropriately in a warm, well insulated infant, could be a cause of some cases of cot death.

Brown fat and sudden death

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Giant cell myocarditis associated with lymphoma

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