Farber disease with prolonged survival

Spinal muscular atrophy-like phenotype in a mouse model of acid ceramidase deficiency

Mutations in ASAH1 have been linked to two allegedly distinct disorders: Farber disease (FD) and spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME). We have previously reported FD-like phenotypes in mice harboring a single amino acid substitution in acid ceramidase (ACDase), P361R, known to be pathogenic in humans (P361R-Farber). Here we describe a mouse model with an SMA-PME-like phenotype (P361R-SMA). P361R-SMA mice live 2-3-times longer than P361R-Farber mice and have different phenotypes including progressive ataxia and bladder dysfunction, which suggests neurological dysfunction. We found profound demyelination, loss of axons, and altered sphingolipid levels in P361R-SMA spinal cords; severe pathology was restricted to the white matter. Our model can serve as a tool to study the pathological effects of ACDase deficiency on the central nervous system and to evaluate potential therapies for SMA-PME.

Acid Ceramidase Deficiency: Bridging Gaps between Clinical Presentation, Mouse Models, and Future Therapeutic Interventions

Farber disease (FD) and spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME) are ultra-rare, autosomal-recessive, acid ceramidase (ACDase) deficiency disorders caused by ASAH1 gene mutations. Currently, 73 different mutations in the ASAH1 gene have been described in humans. These mutations lead to reduced ACDase activity and ceramide (Cer) accumulation in many tissues. Presenting as divergent clinical phenotypes, the symptoms of FD vary depending on central nervous system (CNS) involvement and severity. Classic signs of FD include, but are not limited to, a hoarse voice, distended joints, and lipogranulomas found subcutaneously and in other tissues. Patients with SMA-PME lack the most prominent clinical signs seen in FD. Instead, they demonstrate muscle weakness, tremors, and myoclonic epilepsy. Several ACDase-deficient mouse models have been developed to help elucidate the complex consequences of Cer accumulation. In this review, we compare clinical reports on FD patients and experimental descriptions of ACDase-deficient mouse models. We also discuss clinical presentations, potential therapeutic strategies, and future directions for the study of FD and SMA-PME.

Farber disease in a patient from China

Farber disease (FD) is a rare lysosomal storage disorder caused by mutation of the ASAH1 gene. Classic symptoms of FD include subcutaneous nodules, joint pain and hoarseness. Most patients die during childhood. Here we report a 25-year-old female FD patient with rare osteolytic changes of bilateral hands and toes. Genetic analysis revealed novel compound heterozygous mutations in the ASAH1 gene (c.427T>G and c.358G>C). Further research is needed to elucidate the pathophysiological course.

Hepatic pathology and altered gene transcription in a murine model of acid ceramidase deficiency

Farber disease (FD) is a rare lysosomal storage disorder (LSD) characterized by systemic ceramide accumulation caused by a deficiency in acid ceramidase (ACDase). In its classic form, FD manifests with painful lipogranulomatous nodules in extremities and joints, respiratory complications, and neurological involvement. Hepatosplenomegaly is commonly reported, and severe cases of FD cite liver failure as a cause of early death. Mice homozygous for an orthologous patient mutation in the ACDase gene (Asah1^P361R/P361R) recapitulate the classical form of human FD. In this study, we demonstrate impaired liver function and elevation of various liver injury markers in Asah1^P361R/P361R mice as early as 5 weeks of age. Histopathology analyses demonstrated significant formation and recruitment of foamy macrophages, invasion of neutrophils, progressive tissue fibrosis, increased cell proliferation and death, and significant storage pathology within various liver cell types. Lipidomic analyses revealed alterations to various lipid concentrations in both serum and liver tissue. A significant accumulation of ceramide and other sphingolipids in both liver and hepatocytes was noted. Sphingolipid acyl chains were also altered, with an increase in long acyl chain sphingolipids coinciding with a decrease in ultra-long acyl chains. Hepatocyte transcriptome analyses revealed significantly altered gene transcription. Molecular pathways related to inflammation were found activated, and molecular pathways involved in lipid metabolism were found deactivated. Altered gene transcription within the sphingolipid pathway itself was also observed. The data presented herein demonstrates that deficiency in ACDase results in liver pathology as well as sphingolipid and gene transcription profile changes that lead to impaired liver function.

Acid ceramidase deficiency: Farber disease and SMA-PME

Acid ceramidase (ACDase) deficiency is a spectrum of disorders that includes a rare lysosomal storage disorder called Farber disease (FD) and a rare epileptic disorder called spinal muscular atrophy with progressive myoclonic epilepsy (SMA-PME). Both disorders are caused by mutations in the ASAH1 gene that encodes the lysosomal hydrolase that breaks down the bioactive lipid ceramide. To date, there have been fewer than 200 reported cases of FD and SMA-PME in the literature. Typical textbook manifestations of classical FD include the formation of subcutaneous nodules, accumulation of joint contractures, and development of a hoarse voice. In reality, however, the clinical presentation is much broader. Patients may develop severe pathologies leading to death in infancy or may develop attenuated forms of the disorder wherein they are often misdiagnosed or not diagnosed until adulthood. A clinical variability also exists for SMA-PME, in which patients develop progressive muscle weakness and seizures. Currently, there is no known cure for FD or for SMA-PME. The main treatment is symptom management. In rare cases, treatment may include surgery or hematopoietic stem cell transplantation. Research using disease models has provided insights into the pathology as well as the role of ACDase in the development of these conditions. Recent studies have highlighted possible biomarkers for an effective diagnosis of ACDase deficiency. Ongoing work is being conducted to evaluate the use of recombinant human ACDase (rhACDase) for the treatment of FD. Finally, gene therapy strategies for the treatment of ACDase deficiency are actively being pursued. This review highlights the broad clinical definition and outlines key studies that have improved our understanding of inherited ACDase deficiency-related conditions.

Chronic lung injury and impaired pulmonary function in a mouse model of acid ceramidase deficiency

Farber disease (FD) is a debilitating lysosomal storage disorder (LSD) caused by a deficiency of acid ceramidase (ACDase) activity due to mutations in the gene ASAH1. Patients with ACDase deficiency may develop a spectrum of clinical phenotypes. Severe cases of FD are frequently associated with neurological involvement, failure to thrive, and respiratory complications. Mice homozygous ( Asah1P361R/P361R) for an orthologous patient mutation in Asah1 recapitulate human FD. In this study, we show significant impairment in lung function, including low compliance and increased airway resistance in a mouse model of ACDase deficiency. Impaired lung mechanics in Farber mice resulted in decreased blood oxygenation and increased red blood cell production. Inflammatory cells were recruited to both perivascular and peribronchial areas of the lung. We observed large vacuolated foamy histiocytes that were full of storage material. An increase in vascular permeability led to protein leakage, edema, and impacted surfactant homeostasis in the lungs of Asah1P361R/P361R mice. Bronchial alveolar lavage fluid (BALF) extraction and analysis revealed accumulation of a highly turbid lipoprotein-like substance that was composed in part of surfactants, phospholipids, and ceramides. The phospholipid composition of BALF from Asah1P361R/P361R mice was severely altered, with an increase in both phosphatidylethanolamine (PE) and sphingomyelin (SM). Ceramides were also found at significantly higher levels in both BALF and lung tissue from Asah1P361R/P361R mice when compared with levels from wild-type animals. We demonstrate that a deficiency in ACDase leads to sphingolipid and phospholipid imbalance, chronic lung injury caused by significant inflammation, and increased vascular permeability, leading to impaired lung function.

Successful hematopoietic stem cell transplantation in Farber disease

Farber disease, a lysosomal storage disorder, has a dismal prognosis leading to death with progressive granulomatous inflammation, even in patients without central nervous system involvement (type 2/3). We report the first successful hematopoietic stem cell transplantations in 2 patients with Farber disease type 2/3, resulting in resolution of symptoms.

Bone marrow transplantation for infantile ceramidase deficiency (Farber disease)

Infantile ceramidase deficiency (Farber disease) is an uncommon, progressive lysosomal storage disease characterized by multiple ceramide-containing nodules (lipogranulomata) in the subcutaneous tissue and upper aerodigestive tract, painful periarticular swelling, psychomotor retardation, and varying degrees of ocular, pulmonary or hepatic involvement. Management of Farber disease has been limited to symptomatic supportive care, and few affected infants survive beyond 5 years of age. We performed an allogeneic bone marrow transplant (BMT) from an HLA-identical heterozygous sister in a 9.5-month-old female with minimally symptomatic Farber disease who received a pre-transplant regimen of busulfan and cyclophosphamide. Ceramidase activity in peripheral blood leukocytes increased from 6% before transplant to 44% (donor heterozygote level) by 6 weeks after BMT. By 2 months after transplant, the patient's subcutaneous lipogranulomata, pain on joint motion, and hoarseness had resolved. Despite modest gains in cognitive and language development, hypotonia and delayed motor skills persisted. Gradual loss of circulating donor cells with autologous hematopoietic recovery occurred; VNTR analyses showed 50% donor DNA in peripheral blood cells at 8.5 months after BMT and only 1% at 21 months after transplant. Interestingly, leukocyte ceramidase activity consistently remained in the heterozygous range despite attrition of donor cells in peripheral blood. This novel observation indicates ongoing hydrolase production by non-circulating donor cells, possibly in the mononuclear phagocytic system, and uptake by recipient leukocytes. Although lipogranulomata and hoarseness did not recur, the patient's neurological and neurocognitive status progressively declined. She died 28 months after BMT (age 37.5 months) with pulmonary insufficiency caused by recurrent aspiration pneumonias. Allogeneic BMT improves the peripheral manifestations of infantile ceramidase deficiency, but may not prevent the progressive neurological deterioration, even when carried out in minimally symptomatic patients.

Neurodegenerative course in ceramidase deficiency (Farber disease) correlates with the residual lysosomal ceramide turnover in cultured living patient cells

Farber's lipogranulomatosis is an inborn lipid storage disease characterized by tissue accumulation of ceramide due to deficient activity of lysosomal ceramidase. Symptoms include painful swelling of joints, subcutaneous nodules, a hoarse cry, hepatosplenomegaly and nervous system dysfunction of markedly variable degree. In most cases the neural dysfunction rather than the general dystrophy, seems to limit the duration of Farber disease. We examined whether the severity can be shown as a function of ceramide turnover by lysosomal ceramidase. The lysosomal degradation of sphingomyelin-derived ceramide was studied in situ in patient skin fibroblasts and lymphoid cells loaded with LDL-associated radioactive sphingomyelin. We could show for the first time a significant correlation between the ceramide accumulated in situ and the severity of Farber disease. Our method provides an alternative means for determining ceramide degradation by lysosomal ceramidase, but in intact cells. The relatively simple method is at least of the same diagnostic use for Farber disease as the in vitro assay of acid ceramidase using cell homogenates and may also have some prognostic use.