Heterogeneous molecular behavior in liver tumors (HCC and CCA) of two patients with acute intermittent porphyria.

INTRODUCTION: Acute intermittent porphyria (AIP) is a very rare (orphan) metabolic disorder of porphyrin biosynthesis which is characterized by elevated plasma and urine levels of 5-aminolevulinic acid (5-ALA) and porphobilinogen (PBG). Patients with this disorder which is caused by a germline mutation of the hydroxymethylbilan-synthase (HMBS)-gene have a high risk of primary liver cancer which may be determined by disease activity. The exact mechanism of carcinogenesis of this rare tumor is unknown, however. MATERIALS AND METHODS: We analyzed paraffin-embedded formalin-fixed liver tumor and normal liver specimens of two female AIP patients treated at the Munich EPNET center. One patient had developed hepatocellular carcinoma (HCC), the other intrahepatic cholangiocarcinoma (CCA). Since biallelic inactivation of HMBS had been observed in one study, we used Sanger and next-generation sequencing with a 8 gene porphyria panel plus 6 potential modifier loci to search for mutations in DNA extractions. RESULTS: In the patient with the HCC, we found a second inactivating mutation in the HMBS gene in the tumor but not in the adjacent normal liver tissue. No mutation could be found in the liver tissues of the patient with CCA, however. CONCLUSIONS: Biallelic inactivation of HMBS or protoporphyrinogen-oxidase (PPOX), another enzyme of porphyrin biosynthesis, has been observed in patients with acute porphyrias and liver tumors. We could confirm this in our patient with HCC with a mutation in HMBS but not in the one with CCA. Since 5-ALA can be converted into carcinogenic substances such as 4,5-dioxovaleric acid (DOVA) or 3,6-dihydropyrazine-2,5-dipropanoic acid (= cyclic dimerization product of 5-ALA), local production of these metabolites in hepatic areas with complete loss of HMBS activity may contribute to liver carcinogenesis.

Anisotropy of transcallosal motor fibres indicates functional impairment in children with periventricular leukomalacia.

AIM: In children with bilateral spastic cerebral palsy (CP), periventricular leukomalacia (PVL) is commonly identified on magnetic resonance imaging. We characterized this white matter condition by examining callosal microstructure, interhemispheric inhibitory competence (IIC), and mirror movements. METHOD: We examined seven children (age range 11y 9mo-17y 9mo, median age 15y 10mo, four females, three males) with bilateral spastic CP/PVL (Gross Motor Function Classification System level I or II, Manual Ability Classification System level I) and 12 age-matched controls (age range 11y 7mo-17y 1mo, median age 15y 6mo, seven females, five males). Fractional anisotropy of the transcallosal motor fibres (TCMF) and the corticospinal tract (CST) of both sides were calculated. The parameters of IIC (transcranial magnetic stimulation) and mirror movements were measured using a standardized clinical examination and a computer-based hand motor test. RESULTS: Fractional anisotropy was lower in children with bilateral spastic CP/PVL regarding the TCMF, but not the left or right CST. Resting motor threshold was elevated in children with bilateral spastic CP/PVL whereas measures of IIC tended to be lower. Mirror movements were markedly elevated in bilateral spastic CP/PVL. INTERPRETATION: This study provides new information on different aspects of motor function in children with bilateral spastic CP/PVL. Decreased fractional anisotropy of TCMF is consistent with impairment of hand motor function in children with bilateral spastic CP/PVL. The previously overlooked microstructure of the TCMF may serve as a potential indicator for hand motor function in patients with bilateral spastic CP/PVL.