Smith–Lemli–Opitz syndrome (SLOS) is a cholesterol synthesis disorder, with an etiology of severe malnutrition, which is often excluded from typical differential diagnostic strategies. However, SLOS can be detected during a careful physical examination; thus, it was selected to draw attention to the malnutrition etiology.It was selected to exemplify how an inborn error in cholesterol metabolism can induce malnutrition. A four month old girl was referred to our polyclinic with a diagnosis of severe acute malnutrition since 4 months. She was the only child from a second pregnancy; the first child of her non-consanguineous parents was lost due to an abortion. Physical examination involving weight, height, and head circumference were at third centimeter persentile and below; additionally, dysmorphic facial appearance and syndactyly between the second and third finger of the foot feet was noted. Neuromotor development was normal for her age. Suspecting a phenotype suggesting a congenital problem, a lipid analysis was performed that revealed hypolipidemia. SLOS was considered as a differential diagnosis. Accordingly, the level of biomarker 7 dehydrocholesterol was assessed controlled and was found to be 1772, which was considerably higher than normal (normal < 10 mmol/L). Subsequently, molecular assay revealed pTyr432Cys (c.1295A> G) htr pArg446Trp (c.1336C> T) heterozygous mutation. Steroid hormone levels, bile acid synthesis, fat-soluble vitamin absorption, and central nervous system development may be negatively affected because they were evaluated in detail. No other pathology was detected except for a patent foramen ovale. A replacement therapy comprising of bile acids (ursodeoxycholic acid 15–25 mg/kg/day) and cholesterol (50–100 mg/kg/day) was initiated, along with a cholesterol-rich diet. After 1 month, the patient weighed 5935 g, with a height of 69 cm, head circumference of 38 cm, total cholesterol level of 83 mg/dL, High density lipoprotein (HDL) level of 30 mg/ dL, and Low density lipoprotein (LDL) level of 32 mg/dL. However, the patient’s nutrient intake was not adequate, and percutaneous endoscopic gastrostomy was initiated, following which the patient’s weight and cholesterol levels improved. To reach SLOS diagnosis, it is necessary to conduct full physical examination, including taking out the socks; looking at toe finger structure; evaluating head size, palate, uvula, and external genitals; and observing signs of mental retardation. In routine tests for assessing malnutrition, triglyceride and cholesterol control are not performedassesed. The evaluation of the serum lipid profile should not be overlooked in patients with dysmorphic malnutrition.