Familial hypo-beta-lipoproteinaemia.

A 2-year-old boy investigated because of small stature, had low serum levels of cholesterol (74 mg/100 ml) and β-lipoprotein cholesterol (20 mg/100 ml). Faecal fat, jejunal biopsy, red cell morphology, and plasma growth hormone and thyroxine were normal, and it was concluded that the small stature was hereditary. A family study showed a similar lipoprotein abnormality in the patient's mother; her serum cholesterol was 83 mg/100 ml and β-lipoprotein cholesterol 34 mg/100 ml. Analysis of the β-lipoprotein fraction in both child and mother showed it to have an abnormal lipid composition; the cholesterol/phospholipid ratio was 1·0 and 0·8, respectively (normal 1·7), and within the phospholipid components the proportion of sphingomyelin was markedly reduced (11% and 5%, normal 30%). These findings differ from previous reports that the composition of β-lipoprotein is normal. Familial hypo-β-lipoproteinaemia has been shown to be inherited as an autosomal dominant, and our findings are in agreement. Although a few individuals with this condition have been reported to have some of the features associated with a-β-lipoproteinaemia, neither our patient nor his mother had any gastrointestinal, haematological, or neurological abnormalities.