From a tertiary referral lipid clinic, we evaluated 60 patients (80% female) who had partial lipodystrophy, with diabetes or moderate to severe (type 4 or 5) hypertriglyceridemia. Age, body mass index, untreated fasting plasma cholesterol and triglycerides (mean+standard deviation [SD]) were, respectively, 52.5 ± 14.0 years, 26.2 ± 3.8 kg/m², 6.9 ± 5.0 mmol/L and 11.1+10.0 mmol/L. All subjects consented to DNA analysis. No coding sequence mutations were found in LMNA, PPARG, BSCL2 or AGPAT2 genes encoding nuclear lamin A/C, peroxisome proliferator-activated receptor gamma, seipin or 1-acyl-sn-glycerol-3-phosphate acetyltransferase, respectively.

Two rare heterozygous coding sequence variants in CAV1 were found among the screened patients, I134fsdelA-X137 in one patient and -88delC in another (Figure 1). These frameshift mutations were absent from the genomes of 1063 normolipidemic control subjects. The I134fsdelA-X137 mutation predicted premature termination, with loss of the carboxy terminal half of the protein product. This mutation was subsequently found in the proband's father, who had a similar phenotype. The -88delC mutation occurred within the 5'-untranslated region with a potential effect on the reading frame. The clinical features of the father and daughter with the heterozygous I134fsdelA-X137 mutation and the singleton patient with the heterozygous -88delC mutation are summarized in Table 1.

The history and clinical features of the I134fsdelA-X137 mutation proband (Patient A) and her affected father (Patient B) have been previously reported 10. Briefly, the proband, who was assessed at age 28 years, was a woman of Northern European origin who was wheelchair bound since early adulthood. At birth, she was noted to have a lack of facial and upper body subcutaneous fat, micrognathia and congenital cataracts. Later, diplopia, tinnitus and a central auditory processing defect were noted. She had severe type 5 hyperlipoproteinemia with recurrent pancreatitis; she had insulin resistance but no diabetes. On examination, she was noted to have orthostatic hypotension, a high arched palate, taut skin with sparing of subcutaneous fat on buttocks, hips and thighs. She was noted also to have webbed toes, acanthosis nigricans, retinitis pigmentosa, iris deposits, marked nystagmus, ocular dysmetria, past-pointing on finger-nose testing, dysdiadochokinesis, a spastic-ataxic gait, spontaneous clonus of legs, bilateral Babinski signs, reduced power in the lower extremity and lost vibration sense in a glove-and-stocking distribution. She had leg spasms, a stiff gait, paresthesiae, imbalance and urinary incontinence. Investigations showed lipemic plasma with markedly elevated serum cholesterol (9.3 mmol/L) and triglycerides (20.4 mmol/L). Her father (Patient B), a 55 year old diabetic man of Northern European origin, had similar body fat distribution to his daughter. He also had congenital cataracts and retinitis pigmentosa, but no neurological complaints, and was ambulatory and well-functioning. On examination, he was noted to have absent facial, neck, and limb fat with increased abdominal and lower back subcutaneous fat. He also had decreased sensation in both legs, with normal muscle power and tone; an unsteady narrow-based gait was elicited. He had milder biochemical abnormalities than his daughter, with mild hypertriglyceridemia and no history of pancreatitis. Of note, Patient B's sister (the paternal aunt of Patient A) died from an undefined neurological condition at age 40. Medical records showed a clinical presentation similar to Patient A, with analogous fat redistribution, leg weakness and ataxia beginning at age 18 and requirement for a wheelchair at age 20 10. Patient C, a heterozygote for the CAV1 -88delC mutation, was 35 years old at assessment. He was noted in his early 20's to have redistributed fat stores, with a relative loss of subcutaneous fat on his arms, gluteal region, thighs and calves and increased visceral fat on abdominal ultrasound examination. He had severe hypertriglyceridemia (range 10 to 80 mmol/L) beginning in his late 20's, with recurrent episodes of pancreatitis. He was diagnosed with diabetes at age 33 and currently takes 120 units of insulin daily in addition to fenofibrate 200 mg daily. Physical examination revealed fat redistribution, with no ocular, neurological, dermatologic or musculoskeletal findings.

The exons and intron-exon boundaries of CAV1 were amplified and bi-directionally sequenced using the primers and conditions in Table 2. All coding sequence mutations were confirmed by a second sequencing reaction performed on another day. The frequency of the CAV1 exon 3 I134fsdelA-X137 variant was determined in healthy control subjects using genomic DNA amplification with primers 5'-ATG GAT ACT GAA TAG TGG GTT TTT and 5'-TGT TGC TGT ATT AGC AAC TTG GA. The 509 bp product was digested with restriction enzyme NsiI (New England Biolabs, Mississauga, ON) and fragments were resolved on 2% agarose gels. The digested fragments of the wild-type allele were 280 and 229 base pairs (bp) in size, while the digested fragment of the mutant allele was 509 bp in size. The frequency of the CAV1 exon 1 -88delC variant was determined in healthy control subjects using genomic DNA amplification with primers 5'-AG ATG ATG CAC TGG GAA AA and 5'-CTA GGC CCC CTC TCC ATT AG, with allele specific diagnostic (SNaPShot) primer 5'-GAT CTT GTA TTG TAT GGG GG.