Clinical findings
Clinical data of the three patients are summarized in Table
1, metabolic and genetic data in Table
2.
Table 1
Summary of clinical and laboratory findings of the patients
Relevant medical history |
Pregnancy | HELLP | uneventful | HELLP |
Gestational age | 35 | 39 | 29 |
Features of metabolic decompensation |
Age (months) | 4 | 8 | 5 |
Hypoglycemia | + | – | – |
Lactic acidosis | + | – | + |
Hyperammonemia | + | – | n. a. |
Hepatopathy | + | – | + |
Cardiomyopathy | + | + | + |
Rhabdomyolysis | – | – | + |
Long term complications |
Cardiomyopathy | – | – | – |
Rhabdomyolysis | – | – | + |
Retinopathy | + | – | + |
Table 2
Biomarkers and genetic data of the patients
Patient 1 | | | | | | HADHA gene: c.1528G > C (p.E510Q), homozygous |
2 daysa | 1.62 | (< 0.05) | 0.46 | (< 0.04) | | |
11 daysa | 0.49 | (< 0.05) | 0.29 | (< 0.04) | normal | |
4 monthsb | 15.41 | (< 0.17) | 10.67 | (< 0.10) | elevated | |
Patient 2 | | | | | | HADHB gene: c.1198G > T (p.E400X)/c.442 + 663A > G, compound heterozygous |
2 daysa | 0.35 | (< 0.05) | 0.06 | (< 0.04) | | |
7 daysa | 0.44 | (< 0.05) | 0.08 | (< 0.04) | normal | |
8 monthsb | 0.045 | (< 0.01) | 0.055 | (< 0.01) | elevated | |
Patient 3 | | | | | | HADHA gene: c.1528G > C (p.E510Q), homozygous |
5 daysa | 0.31 | (< 0.12) | 0.47 | (< 0.16) | n.a. | |
5 monthsb | 0.98 | (< 0.10) | 0.74 | (< 0.10) | elevated | |
Patient 1, a boy, was born after 35 weeks of gestation by Caesarian section due to maternal HELLP (haemolysis, elevated liver enzymes, low platelet count) syndrome (birth weight 2120 g). Postnatal adaptation was uneventful. He is the second child of healthy, non-consanguineous parents of Caucasian origin (Germany/Romania). His older brother is healthy. Two former pregnancies of the mother ended in abortions (G4P2).
Newborn screening was performed on day 2, showing elevated concentrations of C16-OH (1.62 μmol/l; cut-off < 0.05 μmol/l) and C18:1-OH (0.46 μmol/l; cut-off < 0.04 μmol/l). A second screening specimen collected on day 11 again showed elevated C16-OH (0.49 μmol/l; cut-off < 0.05 μmol/l) and C18:1-OH (0.29 μmol/l; cut-off < 0.04) compatible with MTP/LCHAD deficiency (Table
2). Additionally, an analysis of organic acids in urine was initiated revealing normal results. Based on the normal excretion of organic acids, the diagnosis of MTP/LCHAD deficiency was considered excluded, and the patient was discharged home from the maternity clinic. A metabolic center had not been contacted.
At the age of 4 months, after an episode of vomiting and reduced food intake, the patient suffered a life-threatening metabolic decompensation. He presented with hypoglycemia, lactic acidosis (lactate 5 mmol/l; reference < 2.1 mmol/l), hyperammonemia (188 μmol/l; reference < 55 μmol/l), hepatopathy (aspartate transaminase 176 U/l, reference < 70 U/l; alanine transaminase 141 U/l, reference < 49 U/l; lactate dehydrogenase 1101 U/l, reference < 570 U/l), and severe hypertrophic cardiomyopathy (N-terminal brain natriuretic peptide 13,445 ng/l; reference < 84 ng/l). He was comatose when admitted to the emergency department of a metabolic center. The patient’s mother recalled the suspicious newborn screening result enabling prompt anabolic treatment including the restriction of long-chain fatty acids. However, the cardiovascular situation initially worsened to cardiogenic shock requiring invasive ventilation and catecholamine treatment. He recovered slowly after treatment in an intensive care unit for more than three weeks. A percutaneous endoscopic gastrostomy (PEG) tube was inserted for continuous feeding at night time and during catabolic situations. In addition, a vascular access port system was implanted due to difficult peripheral venous access.
At the time of metabolic decompensation, analysis of acylcarnitines in plasma again revealed a pattern consistent with MTP/LCHAD deficiency with elevated concentrations of C16-OH (15.41 μmol/l; cut-off < 0.17 μmol/l) and C18:1-OH (10.67 μmol/l; cut-off < 0.1 μmol/l) (Table
2). Urine analysis now showed elevated excretion of dicarboxylic acids. Diagnosis of LCHAD deficiency was confirmed by analysis of enzyme activity in fibroblasts revealing a reduced activity of LCHAD (4 nmol/min x mg protein; reference 34–114 nmol/min x mg) and a normal activity of LCKAT. Sequencing of the
HADHA gene identified the prevalent mutation, c.1528G > C (p.E510Q), in a homozygous state (Table
2) [
32‐
34] .
Patient 1 is now 7 years of age attending regular school. He is on a fat-modified diet strictly reduced in natural (long-chain) fat, enriched with medium-chain triglycerides (MCT), and supplemented with essential fatty acids. He receives continuous feeding during nights over a PEG tube. It was possible to terminate oral medication for cardiac insufficiency one year after metabolic decompensation. As a long-term complication of LCHAD deficiency, he has been diagnosed with early-stage retinopathy.
Patient 2, a boy, was born after 39 weeks of gestation (birth weight 2750 g). Pregnancy and postnatal adaptation were uneventful. He is the third child of healthy, non-consanguineous parents descending from Afghanistan. His older brother and sister are healthy.
Newborn screening was performed on day 2, showing elevated concentrations of C16-OH (0.35 μmol/l; cut-off < 0.05 μmol/l) and C18:1-OH (0.06 μmol/l; cut-off < 0.04 μmol/l) suspicious for MTP/LCHAD deficiency. A second screening sample collected on day 7 confirmed the elevations of C16-OH (0.44 μmol/l; cut-off < 0.05 μmol/l) and C18:1-OH (0.08 μmol/l; cut-off < 0.04 μmol/l). Analysis of organic acids in urine showed normal results (Table
2). Despite the recommendations of the newborn screening laboratory, patient 2 was not referred to a metabolic center, and dietary treatment was not initiated. The parents were informed by the maternity clinic to ensure regular food intake and to present to the primary care doctor at an early stage in case of intercurrent illness. At the age of 2 months, patient 2 was seen at the maternity clinic for clinical and biochemical follow-up. At that time, patient 2 was in good health. The acylcarnitine pattern was again suspicious for MTP/LCHAD deficiency, analysis of organic acids in urine showed an elevated excretion of dicarboxylic acids. Patient 2 was not referred to a metabolic center but was followed by the maternity clinic. At 4 months of age, echocardiography showed symmetric hypertrophy of the cardiac septum. Dietary restriction of long-chain fatty acids and supplementation of medium chain triglycerides (MCT) were initiated. Compliance to treatment was poor. No contact to a metabolic center was made. At 8 months of age, patient 2 presented with progressive dilatative cardiomyopathy and clinical signs of heart insufficiency. Eventually, he was transferred to a metabolic center. Adequate treatment was started immediately with continuous feeding via PEG tube, strict reduction of long-chain fatty acids intake, supplementation of MCT, and oral medications for cardiac insufficiency. Under this treatment, patient 2 improved, and his cardiac function fully recovered.
At the time of first admission to a metabolic center, the concentrations of C16-OH (0.045 μmol/l; reference < 0.01 μmol/l) and C18:1-OH (0.055 μmol/l; reference < 0.01 μmol/l) in plasma were elevated. Molecular analysis of the
HADHB gene revealed two novel mutations (c.1198G > T/c.442 + 663A > G) in a heterozygous state (Table
2). Mutation c.1198G > T (p.E400X) is predicted to result in a premature stop and is absent in the Exome Aggragation Consortium (ExAC, accessed 20 Feb 2018). The transition c.442 + 663A > G in intron 7 has been postulated to show a similar pathogenic mechanism as the described transition c.422 + 614A > G. This transition has been shown to result in a cryptic splice donor spot with insertion of intronic sequences and a premature stop codon [
35,
36]. In combination, these variants most likely will lead to nonsense mediated mRNA decay and finally absence of protein. Testing the patient’s parents for the identified
HADHB mutations in order to prove the heteroallelic state was not covered by the health care system due to the refugee status of the family. To our knowledge, however, there are no reports of symptomatic MTP heterozygotes. Furthermore, molecular analysis of the
HADHA gene did not reveal any mutations. Given the clinical and biochemical phenotype of the patient we strongly assume the mutations identified in the
HADHB gene to be heteroallelic, thus confirming the diagnosis of MTP deficiency.
The patient is now 4 years of age. He is on a fat-modified diet and receives continuous feeding during nights over a PEG tube. It was possible to terminate oral medication for cardiac insufficiency one year after initial decompensation. So far, he experienced no long-term complications from MTP deficiency.
Patient 3, a boy, is the third child of healthy, non-consanguineous parents of Caucasian origin (Austria). His older brother and sister are healthy. One former pregnancy of the mother ended in an abortion (G4P3). He was born after 29 weeks of gestation by urgent Caesarian section due to maternal HELLP syndrome (birth weight 1040 g). He required non-invasive ventilation for 3 days (FiO2 0.21) due to respiratory distress syndrome and received analeptic treatment with caffeine until day 19 of life. Parenteral nutrition was administered for 8 days. In addition, age-appropriate enteral nutrition was introduced.
Newborn screening was performed on day 5 and considered normal. Retrospective review revealed that concentrations of C16-OH (0.31 μmol/l; cut-off < 0.12 μmol/l) and C18:1-OH (0.47 μmol/l; cut-off < 0.10 μmol/l) were moderately elevated (Table
2) but did not prompt further diagnostic work-up due to normal secondary markers and normal analyte ratios. A second screening specimen after 14 days of life, recommended for infants prior to 32 weeks of gestation, was not obtained for unknown reasons.
At 5 months of age, patient 3 suffered a severe metabolic decompensation after an episode of vomiting and reduced food intake. He presented with mild lactic acidosis (3.6 mmol/l; reference < 2.1 mmo/l), hepatopathy (aspartate transaminase 614 U/l, reference 10–50 U/L; alanine transaminase 266 U/l, reference 6–53 U/l; partial thromboplastin time 178 s, reference 28–43 sec; prothrombin time 47%, reference 70–130%; fibrinogen 83 mg/dl, reference 150–380 mg/dl; antithrombin III 51%, reference 84–124%), rhabdomyolysis (creatine kinase 485 U/l; reference 41–330 U/l) and dilated cardiomyopathy (N-terminal brain natriuretic peptide 5468 ng/l; reference < 84 ng/l). The patient was admitted to a metabolic center. Biomarker analysis showed elevated concentrations of C16-OH (0.98 μmol/l; cut-off < 0.10 μmol/l) and C18:1-OH (0.74 μmol/l; cut-off < 0.10 μmol/l) in plasma (Table
2) as well as elevated excretion of dicarboxylic acids in urine. Anabolic treatment including MCT supplementation, strict restriction of long-chain fatty acids, as well as oral medications for cardiac insufficiency were initiated immediately. Under this treatment, the patient fully recovered.
Diagnosis of LCHAD deficiency was confirmed by molecular analysis of the
HADHA gene revealing the prevalent mutation, c.1528G > C (p.E510Q), in a homozygous state (Table
2) [
32‐
34]. Patient 3 is now 9 years of age. He is on a fat-modified diet and receives continuous feeding during nights over a PEG tube. It was possible to terminate oral medication for cardiac insufficiency one year after initial decompensation. Despite good compliance to treatment, he suffered from multiple episodes of rhabdomyolysis. In addition, he has been diagnosed with retinopathy. This patient was previously described by Karall et al. [
9].