Subcutaneous Fat Necrosis of Newborn: An Atypical Presentation.

Sir,

A full-term male baby weighing 3 kg born by vaginal delivery was referred at 18 h of age with respiratory distress. There was a history of perinatal asphyxia requiring resuscitation and meconium staining of liquor. In view of severe respiratory distress, the baby was intubated and ventilated. Chest X-ray showed few bilateral infiltrates suggestive of meconium aspiration syndrome. On day 4, the baby developed an erythematous rash over the back, and by the 7th day, it progressed to violaceous induration [Figures 1 and 2] Dermatology consultation was sought, and diagnosis of cellulitis was considered. On day 8, the infant had multiple brief episodes of convulsion managed with anticonvulsants. Cranial USG and MRI revealed intraventricular hemorrhage and bilateral periventricular changes consistent with perinatal hypoxia. By the 11th day, lesions progressed to multiple red, soft, fluctuant swellings, suggesting abscess formation. The lesions coalesced to form voluminous collection with inflamed overlying skin and surrounding area [Figure 3]. The baby was weaned off ventilator after 48 h. CBC at admission revealed Hb 14.9 g/dL, TLC 7200, platelets 61,000; CRP was negative. Blood counts on day 4 at manifestation of skin lesions showed drop in platelet count to 31,000 and CRP 6 mg/dl (0–8 mg/dl). Broad-spectrum antibiotics were commenced after sending blood culture as there was concern of sepsis. Ultrasonography showed hyperechoic subcutaneous tissue. Investigations on day 7 revealed Hb 15.2 g/dL, TLC 10,200, platelet 71,000, and quantitative CRP 158 mg/dL. Serum calcium was 10.6 mg/dl (8.8–11 mg/dl), ionic calcium 4.8 mmol/l (2–2.7 mmol/l), triglycerides 115 mg/dl. There was persistent thrombocytopenia on serial blood counts. USG at this point revealed increased echogenicity of subcutaneous fat with two loculated collections measuring 12 mm × 10 mm and 10 mm × 8 mm suggestive of subcutaneous fat necrosis with liquefaction. Blood cultures were sterile. Large collection necessitated needle aspiration, which was done under ultrasound guidance. Culture yielded no growth. There was white chalky pus-like discharge from the fluctuant swellings for few days. Skin biopsy revealed subcutaneous tissue showing necrosis of adipocytes and infiltration by histiocytes and mononuclear cells. Some adipocytes showed needle-shaped clefts in radial arrangements, confirming the diagnosis of subcutaneous fat necrosis [Figure 4]. Platelet count and CRP normalized by 3 weeks. Calcium normalized by 4 weeks. Baby was discharged on day 34. The skin lesions regressed and complete resolution occurred around 6 weeks with scarring. Serum calcium repeated on the last follow-up at 3 months was normal.

Figure 1

Erythematous lesion on the back

Figure 2

Purple violaceous nodules and cystic swellings

Figure 3

Large fluctuant collections

Figure 4

Haematoxylin and eosin staining, ×400 showing A) Areas of necrosed adipocytes with needle shaped clefts B) Lipid laden histiocytes

Subcutaneous fat necrosis is a form of benign lobular panniculitis affecting term or post-term neonates.[124]

Leukocytosis, positive CRP, and low platelet count with cellulitis-like picture favored the initial diagnosis of neonatal sepsis in our case. Diagnosis of SCFN was first considered when ultrasonic evaluation revealed ill-defined areas of increased echogenicity in the subcutaneous fat with loculated collections and normal underlying muscles. Skin biopsy confirmed the diagnosis. USG with Doppler is a less invasive alternative to biopsy for diagnosis and shows high echo signal with or without calcifications and increased blood flow.[5] Possible differential diagnoses to be considered include bacterial cellulitis, erysipelas, sclerema neonatorum, and cold panniculitis.[3] In pyogenic abscess, the infant is often febrile or ill. SCFN can be a close mimic of cellulitis and sepsis; the clinical picture of an otherwise well child with a history of perinatal hypoxia is supportive. Diagnosis can be confirmed by skin biopsy showing characteristic findings of fat necrosis, radially arranged needle-shaped crystals in fat cells, granulomatous infiltrates composed of lymphocytes, macrophages, and giant cells.

Clinicians should be aware of the association between SCFN and perinatal complications. Ultrasonography and Doppler studies can help diagnose this unusual entity and preclude unnecessary biopsy.

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Conflicts of interest

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