Background. The authors present a case report of two brothers presenting severe cachectic features of unknown cause.
Patient 1 currently 3,7 years old; was born at 34 weeks gestational age (IV pregnancy III childbirth delivery by C-section) birth weight: 2750g - 75th pc; birth length 48cm – 75th pc). Patient 2 currently 3 months old who was born at 33 weeks gestational age (pregnancy V childbirth IV delivery by C-section birth weight: birth weight: 1980g -  25th-50th pc; birth length 41cm – 10th -25th pc). Both patients were born following pregnancies complicated by HELLP syndrome. For 24 hours after birth they needed respiratory support due to respiratory insufficiency. 
In both cases no weight and length gain with progressing malnutrition was observed since birth. Regular diet provoked severe abdominal pain and total parenteral nutrition (TPN) was introduced. Hirschsprung disease was excluded. 1st patient underwent laparotomies, resulting in colostomy, and later ileostomy.  Despite high caloric intake with TPN (up to 125 kcal/kg/day) no weight gain was observed, the 2nd patient was malnourished and dependent on continuous parenteral nutrition infusion. 
Methods and results
Performed biochemical (endocrinology, proteinogram, capillary gas chromatography-mass spectrometry, tandem mass spectrometry, carnitine in serum and urine; plasma lactic acid; plasma pyruvic acid) were within the normal range. Colonoscopy, gastroscopy and histopatological tests were normal. Neuroimaging with MRI showed not changes. 
Presented set of symptoms and clinical outcome in brothers suggests genetic background (Smith-Lemli-Opitz syndrome, Silver Russel syndrome, SHORT syndrome, Marshall-Smith syndrome, Opitz-Kavereggia syndrome, Costello syndrome, lipodystrophy were excluded). Whole-Exome Sequencing was inconclusive.

FAMILIAL MARASMUS SYNDROME OF UNKNOWN CAUSE