Lipoid Proteinosis Due to Homozygous Deletion Mutation (c.735delTG) in the ECM1 Gene Presents with Seizures and Hoarseness but No Skin Involvement

Hassan Vahidnezhad, Leila Youssefian, Abbas Tafakhori, Qiaoli Li, Jouni Uitto,?,Fatemeh Vand Rajabpour, Morteza Pishnamazi, Amirhossein Modabbernia, Mina Tabrizi,?

1Molecular Medicine Division, Biotechnology Research Center, Pasteur Institute of Iran, Tehran 14167, Iran; 2Department of Medical Genetics, School of Medicine, Tehran University of Medical Sciences, Tehran 14167, Iran; 3Department of Dermatology and Cutaneous Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA; 4Department of Neurology, Imam Khomeini Hospital, Tehran University of Medical Sciences, Tehran 14167, Iran; 5Research Center for Molecular and Cellular Imaging, Tehran University of Medical Sciences, Tehran 14167, Iran; 6Department of Psychiatry, Icahn School of Medicine at Mount Sinai, New York 10029, USA.

Introduction

Lipoid proteinosis (LP) is a rare autosomal recessive genodermatosis characterized by deposition of amorphous hyaline material in the skin, mucous membranes, and internal organs.1,2The diagnosis is usually made by cutaneous manifestations, confirmed by characteristic histopathology depicting reduplication of the basal lamina.3The characteristic clinical findings include generalized stiffening and scarring of the skin and mucosa and infiltration of the tongue,and the underlying frenulum limits the patients’ ability to protrude their tongue.Infiltration of the vocal cords leads to characteristic hoarseness of voice, often the first diagnostic sign of the disease in early infancy or in the first year of life.Another characteristic sign is development of multiple beaded papules along the eyelid margins. The cutaneous findings are often associated with neurological signs and symptoms manifesting with epilepsy and neuropsychological abnormalities due to calcification of temporal lobes or hippocampi of the brain.4

LP is caused by mutations in the ECM1 gene on chromosome 1q21, encoding the extracellular matrix protein 1 (ECM1) which is present in four different isoforms due to alternative splicing. In this report we describe an Iranian LP patient with seizures and hoarseness, but with no evidence of skin involvement.

Case report

The proband, a 16-year old female, had partial seizures with lip smacking, staring, and impaired consciousness lasting for 30-40seconds since the age of 5 years.Hoarseness of voice had been present at least since 4 years of age.She was born to first cousins once removed parents(Fig.1A).On physical examination,a normally appearing female corresponding to her age was noted. Careful examination failed to identify any characteristic skin lesions,including scarring,eyelid papules,skin infiltration,or verrucous lesions on the knees and elbow (Fig. 1B).Inspection of nasal mucosa, lips, teeth, and ears revealed no abnormalities. Ophthalmologic examination revealed no pathology in the optic discs.She had a younger brother affected with scarring of his skin. Neurological examination of the proband revealed extraocular movements of the eyes, but the corneal reflex and temporal and masseter muscle strength were normal. MRI and CT scan showed significant calcification and atrophy of the bilateral amygdales, a finding associated with LP. Thus, on the basis of hoarseness and neurological findings, even in the absence of cutaneous manifestations,the clinical diagnosis of LP was made.

To confirm the diagnosis at the genomic level,DNA was isolated from peripheral blood samples from the proband,her younger brother, and the parents, after having obtained an informed consent. All 10 exons and the flanking intronic sequences of the ECM1 gene were amplified by PCR using primer pairs and conditions described previously.5Sequencing of the PCR products identified in the proband and her younger brother a homozygous deletion mutation,c.735delTG,in exon 7 of ECM1(Fig.1).This 2-bp deletion results in frameshift and generates a premature termination codon UGA at the site of deletion (p.C245X). The parents of the proband were heterozygous carriers of the same mutation, reflecting consanguinity in the family.

Discussion

Examination of the LP mutation database revealed the presence of 67 distinct mutations. The homozygous c.735delTG mutation was previously reported in a Turkish patient with LP presenting with hoarseness and varicelliform scars but no history of seizures.5However,there was radiographic evidence of temporal lobe calcification in the brain. In both families, the probands had younger siblings harboring the same mutation and presenting with hoarseness and skin involvement. Previously,a 39-year-old female was diagnosed with LP based on severe neurological symptoms since 5 years of age,including unilateral headaches and complex seizures.6Careful skin examination revealed thickened skin at the hands,elbows,and face;however,these changes were very mild and had not been previously noted by the patient,her relatives, or healthcare providers. This patient had a homozygous nonsense mutation p.R243X,which has been reported previously in a patient manifesting with hoarseness and skin findings without any neurological findings.5

Figure 1. A family pedigree with the lipoid proteinosis,face and brain MRI of the proband,and the result of the sequencing of the ECM1 gene.(A)The pedigree is a first cousin once removed with two affected children.(B)Patient does not show typical skin findings of lipoid proteinosis.(C)FLAIR image of patient’s brain showing calcification of amygdala(arrows).(D)The homozygous deletion mutation,c.735delTG,in exon 7 was found in affected patients in this study in comparison to normal sequence of the ECM1 gene.

Previous observations on LP, including our recent studies on Iranian patients with LP,7have demonstrated considerable phenotypic variability as also noted in this study, the proband having no apparent cutaneous findings, while the younger brother presented with extensive skin involvement. Furthermore, comparison of our proband with the individuals in the family reported by Hamada et al.,5with the same genetic mutation,revealed different phenotypic presentations. Collectively, these observations, together with our patient reported here,illustrate the phenotypic spectrum of LP with varied involvement of different organ systems. The reasons for such variability are currently unknown but may reflect the effects of modifier genes, epigenetic factors, and/or environmental influence.

In summary, we present an unusual case of lipoid proteinosis with hoarse voice and neurological manifestations but without skin involvement. The patient had homozygous c.735delTG mutation in the ECM1 gene. This patient illustrates that the diagnosis of LP should be considered in some patients with neurological finding and hoarseness even in the absence of skin findings.

Acknowledgements

Carol Kelly assisted in manuscript preparation.