subcutaneous fat necrosis ( scfn ) of the newborn is a rare inflammatory disorder of the fat tissue presenting in term and postterm infants 1 , consisting in a lobular form of panniculitis associated to painful , hard , and erythematous scfn usually has a favorable prognosis , with complete autoresolution of subcutaneous lesions within several weeks or months , but it may also be complicated by serious metabolic alterations 3 . patient 1 : subcutaneous fat necrosis ( scfn ) hard nodules covered by erythematous skin , localized on the right arm and on the right armpit . patient 2 : purplish , indolent , infiltrated erythematous plaque on the upper arm ( day # 4 of life ) , consistent with scfn . a male term newborn was delivered vaginally at 38 + 2 gestational weeks after labor induction for fetal macrosomia . apgar score was 1 , 5 , and 8 at 1 , 5 , and 10 min , respectively . cord blood gas analysis showed metabolic acidosis ( ph 7.12 , pco 
 2 36 mmhg , hco3 11.7 mmol / l , be 16.7 mmol / l ) . in the first hours after admission to our neonatal intensive care unit ( nicu ) other laboratory results included : alt 229 u / l , cpk 2105 u / l , troponin i 0.074 ng / ml , creatinine 0.82 mg / dl , blood urea nitrogen 29 mg / dl , calcium 10.4 mg / dl . there were no neurological complications . on day # 11 of life , the patient presented with painful subcutaneous hard nodules covered by erythematous skin . these lesions were localized on the right arm and on the right armpit ( fig . serum calcium was slightly increased ( 11.2 mg / dl ) at this time point ; further monitoring showed spontaneous normalization of serum calcium , which remained normal post discharge . on the occasion of the followup visit 3 months post discharge , the baby was in good clinical condition with an appropriatetoage neurological development . a fullterm infant girl ( 40 + 4 gestational weeks ) was born by cesarean section for mechanical dystocia with premature rupture of membranes ( prom ) 24 h before , with stained amniotic fluid . her mother had fever in the postpartum and her blood culture turned positive for escherichia coli , so she was administered antibiotic treatment . the baby 's birth weight was 3940 g ( 90th97th percentile , i.e. , large for gestational age [ lga ] ) , length was 50.5 cm ( 50th75th percentile ) , and head circumference was 35 cm ( 50th75th percentile ) . soon after birth , the patient developed severe perinatal distress , which rapidly improved with noninvasive ventilatory support in delivery room . apgar score was 1 , 4 , and 9 at 1 , 5 , and 10 min , respectively . arterial cord blood gas analysis showed ph 7.05 , pco 
 2 69 mmhg , be 12.3 mmol / l , lactate 7.8 mmol / l . on day # 2 of life , an infiltrated erythematous plaque was observed on the right arm , this lesion turned into a purplish hue 2 days later ( fig . predischarge blood tests performed on day # 7 of life showed mild hypercalcemia ( calcium 11.1 mg / dl ) with normal platelet count . basing on clinical history , physical examination , and biochemical parameters , the erythematous lesion of the arm was diagnosed as scfn . the neurological outcome was favorable , as assessed on the occasion of the 3 months followup visit postdischarge . subcutaneous fat necrosis of the newborn ( scfn ) represents a benign condition occurring in the neonatal period 4 , characterized by inflammation and necrosis of subcutaneous fat tissue and typically presenting with subcutaneous purplebluish hard nodules ( see figs . 1 and 2 ) 5 . lesions may appear isolated or clustered and are typically located on shoulders , back , buttocks , and face 6 ; nodules may evolve into subcutaneous calcifications 5 . etiology of this disorder is unknown , but it is linked to multiple neonatal and maternal risk factors ( table 1 ) 2 . physiopathology of scfn may involve a precocious phase of impaired tissue perfusion with subsequent tissue hypoxia leading to crystallization of neonatal subcutaneous fat , followed by tissue necrosis and granulomatous reaction 6 . neonatal and maternal risk factors for scfn of the newborn umbilical cord prolapse therapeutic hypothermia maternal diabetes mellitus maternal medications ( calcium channel blockers , cocaine ) smoking or exposure to passive smoking during pregnancy maternofetal rh incompatibility subcutaneous fat necrosis is usually a benign condition . nevertheless , it may be associated with thrombocytopenia , hypoglycemia , hypercalcemia , and hypertriglyceridemia 2 ; these metabolic derangements may , in turn , represent a possible risk for serious complications 2 . thrombocytopenia is usually synchronous with the appearance of subcutaneous nodules , and it is possibly caused by peripheral platelet sequestration into the lesions 7 , 8 . hypoglycemia is reported in literature as another risk factor linked to scfn , but rather than being a cause of scfn it seems to be itself a consequence of hypoxia 1 . hypercalcemia is found in 25% of cases 5 and represents the most serious potential complication , associated with significant mortality and morbidity 1 . the first 6 weeks of life represent the time frame at highest risk for clinically significant hypercalcemia in scfn , with 40% of cases occurring in this lapse of time 9 . usually , serum calcium starts to rise as scfn lesions begin to regress ; sometimes , hypercalcemia is already detectable before the onset of subcutaneous lesions 5 . neonates with hypercalcemia tend to present with lethargy , hypotonia , irritability , vomiting , polyuria , polydipsia , constipation , and dehydration 8 . hypercalcemia is caused by increased prostaglandin activity , release of calcium from necrotic fat tissue , and increased secretion of 1,25dihydroxyvitamin d3 from subcutaneous lesions , leading to an increased intestinal uptake of calcium 2 . if left untreated , moderate to severe hypercalcemia may lead to complications as nephrocalcinosis , nephrolithiasis , renal failure ; calcification of falx cerebri , skin , myocardium , and gastric mucosa may also occur 2 , 8 . treatment of hypercalcemia consists of hyperhydration and diet with low levels of calcium and vitamin d ; sometimes , other drugs like furosemide and prednisolone are needed to decrease serum calcium 2 ; bisphosphonates ( e.g. , etidronate ) may also be employed to treat moderate to severe hypercalcemia when other measures have proven ineffective 10 . in children with a personal history of scfn it is recommended to evaluate serum calcium levels periodically until the age of 6 months 8 . however , it may be complicated by a number of metabolic alterations like thrombocytopenia , hypoglycemia , hypercalcemia , and hypertriglyceridemia . it is pivotal to monitor newborns with scfn to avoid the risk of serious complications , with particular reference to hypercalcemia . regular monitoring of serum calcium is recommended until the age of 6 months , in infants with personal history of scfn .
key clinical messagesubcutaneous fat necrosis ( scfn ) is a rare fat tissue inflammation of the newborn . 
 risk factors include cord prolapse , perinatal asphyxia , therapeutic hypothermia , meconium aspiration , and sepsis . when present , hypercalcemia comes with lethargy , hypotonia , irritability , vomiting , polyuria , polydipsia , constipation , and dehydration . 
 kidney injury must be avoided . 
 scfn is often completely autoresolutive .