autosomal recessive

Alkaptonuria

Clinical Characteristics
Ocular Features: 

Ocular signs of this disease are present in two out of three patients.  Black or bluish pigmented patches may be noted in the sclerae by the fourth decade. The pigmentation is most evident just anterior to the insertion of the medial and lateral rectus muscles.  It is claimed that brown pigment spots resembling 'oil drops' near the opaque portion of the limbus are diagnostic but they are often not present until the 4th or 5th decades.  Nevertheless, these ocular signs on average precede systemic signs by about 15 years and are therefore diagnostically useful.  The pigmentation has no impact on vision. Hyperpigmentation of the anterior chamber angle with elevated intraocular pressure has been reported.  An increased incidence of central vein occlusion has been suggested.  Progressive astigmatism is sometimes seen.  Staining of the tarsal plates may be seen in the eyelids.

Systemic Features: 

Ochronosis (dark pigmentation in connective tissue) as the result of homogentisic acid (HGA) accumulation is a useful sign but does not appear until the 4th decade.  As a result the joint cartilage becomes fragile leading to disabling and chronic symptoms of arthritis especially in the spine and large joints.  Symptoms usually begin in the third or fourth decade and the degeneration of the ochronotic intervertebral disks may result in significant loss of height.  Back pain, kyphosis, and decreased lumbar flexion are common.  Usually smaller joints such as those of the digits are not affected sufficiently to cause symptoms.

Tendons, ligaments, and other fibrous tissue such as sclerae and heart valves are all susceptible to degenerative changes.  The discoloration in skin hue can also be seen in the axillae, nail beds, pinnae, forehead, tympanic membranes, genital areas, and buccal mucosa.  Clothing may become stained from discolored perspiration.

HGA in the urine oxidizes and turns dark and parents may note staining of diapers in the newborn period.  The urine also becomes alkaline.  Plasma levels of HGA are also elevated.  Urolithiasis may occur.

Genetics

This metabolic disease is among the first inborn errors of metabolism described.  Virchow had early described the yellowish discoloration of connective tissue seen under the microscope.  William Bateson at the beginning of the 20th century suggested the heritability of this condition to the British physician Sir Archibald Garrod who then described this syndrome in 1902 as the first human disease whose transmission pattern conformed to mendelian autosomal recessive inheritance based on his understanding of Mendel's laws.

Homozygosity of mutations in the HGD gene (3q13.33) coding for homogentisate 1,2-dioxygenase is responsible for the phenotype.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Nitisinone reduces the production of HGA and can lower urinary levels up to 95% but may lead to elevated plasma tyrosine that rarely results in the deposition of corneal crystals.  Long-term benefits of nitisinone remain unknown. Others have tried dietary reduction of tyrosine and phenylalanine with reduction in HGA levels but the long term impact on the rate of tissue degradation remains unknown.    

Additional treatment is directed at specific damaged sites.  Calcified valves (often aortic) may need to be replaced.  Large joints such as hips, shoulders, and knees often require replacement for pain relief.  Stones in the urinary tract may need to be removed.  Ophthalmologists should keep such patients under observation for progressive astigmatism and the risk of elevated intraocular pressure.

It may be prudent to avoid contact sports and minimize heavy weight lifting to limit trauma to joint cartilage.

References
Article Title: 

Natural history of alkaptonuria

Phornphutkul C, Introne WJ, Perry MB, Bernardini I, Murphey MD, Fitzpatrick DL, Anderson PD, Huizing M, Anikster Y, Gerber LH, Gahl WA. Natural history of alkaptonuria. N Engl J Med. 2002 Dec 26;347(26):2111-21.

PubMed ID: 
12501223

The molecular basis of alkaptonuria

Fernandez-Canon JM, Granadino B, Beltran-Valero de Bernabe D, Renedo M, Fernandez-Ruiz E, Penalva MA, Rodriguez de Cordoba S. The molecular basis of alkaptonuria. Nat Genet. 1996 Sep;14(1):19-24.

PubMed ID: 
8782815

Pseudoxanthoma Elasticum-Like Disease

Clinical Characteristics
Ocular Features: 

Retinitis pigmentosa has been diagnosed clinically and confirmed by ERG studies in some patients. The fundi in a few individuals have the typical angioid streaks and/or peau d’orange changes. The impact on visual acuity and its prognosis has not been systematically studied.

Systemic Features: 

The skin changes resulting from fragmentation and aberrant mineralization of connective tissue, particularly elastic fibers, resemble those seem in classic pseudoxanthoma elasticum. These include the presence of yellowish papules or leathery plaques with dot-like depressions (‘chicken skin’). However, the skin changes are more widespread and involve trunk as well as limbs and flexural areas. Ultrastructurally the elastic fibers are more severely fragmented than those in classic PXE.

Many patients in addition have deficiencies in vitamin K-dependent clotting factors such as II, VII, IX, and X. Epistaxis, spontaneous gingival bleeding and severe vaginal hemorrhages may occur. Cerebral aneurysms, vascular occlusions, and atherosclerotic plaques in the lower extremities have been reported in a few patients.

Genetics

Classic pseudoxanthoma elasticum is due to homozygous mutations in the ABCC6 (ATP-binding cassette subfamily C member 6) gene. However, in the PXE-like condition described here homozygous or compound heterozygous mutations in the GGCX (gamma-glutamyl carboxylase) gene (2p11.2) are responsible. Some heterozygous GGCX individuals in families with this genotype who are also heterozygous for ABCC6 mutations (doubly heterozygous) may have similar skin features. Thus the condition described here may also be a digenic disorder in some individuals.

Pseudoxanthoma elasticum-like disease is an autosomal recessive disorder.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

There is no treatment for the connective tissue defect but individual problems such as subretinal neovascularization, hemorrhages, and vascular occlusions may respond to appropriate therapy.

References
Article Title: 

Retinopathy with Neutropenia

Clinical Characteristics
Ocular Features: 

Pigmentary retinopathy was reported in a 25 year old female with moderately reduced visual acuity. Rare bone spicules pigment deposits were present in the periphery and macular edema was noted. Severely reduced scotopic and photopic responses were recorded.

Systemic Features: 

The single reported individual had congenital neutropenia and microcephaly. She had evident growth retardation and microcephaly at birth with subsequent recurrent upper respiratory infections and gingivitis. Speech and motor development were normal. Short stature was noted as well. The limbs were described as slender as in Cohen syndrome (216550) but no truncal obesity or joint hypermobility was present. The facial dysmorphism only vaguely resembled that found in Cohen syndrome (216550).

Genetics

This is a newly described condition whose unique identity remains to be established since only a single patient has been reported. This patient carried two heterozygous splicing mutations in the same VPS13B gene, the same gene in which more than 100 homozygous mutations have been found in individuals with Cohen syndrome (216550). Each parent carried a different splicing mutation in VPS13B.

Cohen syndrome (216550) however, has additional phenotypic features such as truncal obesity, intellectual disabilities, intermittent neutropenia, microcephaly, facial dysmorphism, myopia, and progressive chorioretinal dystrophy. Variable amounts of neutropenia were observed from age 5 years but the marrow was normocellular in appearance.

Isolated retinopathy with neutropenia may or may not be an autosomal recessive variant of Cohen syndrome (216550).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported.

References
Article Title: 

External Ophthalmoplegia, Facial Weakness, and Malignant Hyperthermia

Clinical Characteristics
Ocular Features: 

A subset of patients with malignant hyperthermia susceptibility (MHS) secondary to mutations in RYR1 has congenital ophthalmoplegia and ptosis.   Magnetic resonance imaging may reveal hypoplasia of extraocular muscles and intraorbital cranial nerves.

Systemic Features: 

The weakness in extraocular and levator muscles is sometimes associated with more generalized myopathy of a variable degree.  The myopathy may be progressive and individuals with extensive skeletal muscle weakness may have respiratory insufficiency and scoliosis. The clinical spectrum is broad and there is no consistent pattern in the degree of skeletal muscle weakness associated with ocular muscle involvement.  This may be explained in part by the variety of myopathies found among patients with mutations in RYR1 such as:  central core disease, multiminicore disease, congenital fiber type disproportion, centronuclear myopathy, and nemaline myopathy.

Malignant hyperthermia due to mutations in RYR1 is most commonly inherited as an autosomal dominant trait precipitated by exposure to certain volatile anesthetic agents such as halothane, isoflurane, and enflurane used in association with succinylcholine during general anesthesia.  Patients may experience acidosis, muscle rigidity, rhabdomyolysis and tachycardia with arrhythmias.  Myoglobinuria may lead to renal failure.

Exercise-induced heat stress rarely precipitates malignant hyperthermia.

Genetics

Ptosis, ophthalmoplegia, and susceptibility to malignant hyperthermia can occur as separate heritable conditions and it is uncommon for them to coexist as in the MHS1 syndrome described here.  Due to the heterogeneous signs of muscle disease reported among and between families, it is likely that MHS1 consists of more than one disorder.  Mutations in RYR1 are commonly associated with susceptibility to malignant hyperthermia while the co-occurrence of skeletal muscle disease is inconsistent and involvement of extraocular muscles is even rarer.

There is good evidence that at least 6 types of MHS exist.  A large number of responsible mutations in 2 genes, RYR1 (19q13.2) and CACNA1S (1q32.1), have been identified and there is good evidence that at least 4 additional loci exist.  Mutations in RYR1 are responsible for MHS1 and account for approximately 70% of susceptible individuals.  Families with both autosomal dominant and autosomal recessive inheritance patterns have been reported.  

It is not understood why some families with MHS1 have ocular and skeletal muscle abnormalities while others do not.  External ophthalmoplegia is most often secondary to mutations in mitochondrial DNA but the importance of presurgical recognition of the risk of malignant hyperthermia suggests that pre-surgery gene screening for RYR1 in such patients is warranted.

Pedigree: 
Autosomal dominant
Autosomal recessive
Treatment
Treatment Options: 

The best treatment is prevention by using alternate anesthetic agents if the risk is recognized preoperatively.  Temperature should be monitored in all patients undergoing general anesthesia since prompt recognition of hyperthermia is essential.  Inhalation agents and succinylcholine must be discontinued and dantrolene sodium should be given promptly.  Metabolic abnormalities must be corrected and both external and internal body cooling should be initiated immediately.  Intravascular coagulation is an additional risk and coagulation profiles should be obtained.

A positive family history of MHS requires pre-anesthesia gene testing but failure to detect a mutation in known genes does not rule out susceptibility.

Ptosis surgery may be helpful in selected patients.

References
Article Title: 

Recessive RYR1 mutations cause unusual congenital myopathy with prominent nuclear internalization and large areas of myofibrillar disorganization

Bevilacqua JA, Monnier N, Bitoun M, Eymard B, Ferreiro A, Monges S, Lubieniecki F, Taratuto AL, Laquerriere A, Claeys KG, Marty I, Fardeau M, Guicheney P, Lunardi J, Romero NB. Recessive RYR1 mutations cause unusual congenital myopathy with prominent nuclear internalization and large areas of myofibrillar disorganization. Neuropathol Appl Neurobiol. 2011 Apr;37(3):271-84.

PubMed ID: 
21062345

Albinism, Oculocutaneous, Type VII

Clinical Characteristics
Ocular Features: 

Nystagmus and iris transillumination are present in all family members studied.  VEP studies show asymmetric decussation of axons in the chiasm.  The peripheral retina may have striking hypopigmentation. OCT reveals hypoplasia of the foveal region.   Photophobia is not a significant problem. Visual acuity is mildly to moderately reduced.

Systemic Features: 

Homozygous individuals are lighter in complexion than other family members. Hair color ranges from pale blond to dark brown.

Genetics

Homozygous mutations in the C10orf11 gene (10q22.2-q22.3) are responsible for the phenotype of this autosomal recessive condition.  The gene is active in melanocyte differentiation.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment for the hypopigmentation has been reported.  Visual function might be improved with low vision aids.

References
Article Title: 

Increasing the complexity: new genes and new types of albinism

Montoliu L, Gronskov K, Wei AH, Martinez-Garcia M, Fernandez A, Arveiler B, Morice-Picard F, Riazuddin S, Suzuki T, Ahmed ZM, Rosenberg T, Li W. Increasing the complexity: new genes and new types of albinism. Pigment Cell Melanoma Res. 2014 Jan;27(1):11-18. Review.

PubMed ID: 
24066960

Albinism, Oculocutaneous, Type VI

Clinical Characteristics
Ocular Features: 

Nystagmus is usually present from birth and visual acuity is in the range of 20/100.  There is marked hypopigmentation in the retina and the iris often transilluminates.  OCT usually shows foveal flattening consistent with hypoplasia.  Most patients experience severe photophobia and many have strabismus.

Systemic Features: 

There is usually complete loss or a severe reduction of melanin in skin, hair, and eyes.  Hair color is blond but may become tinged with brown in older individuals.  The skin may have pigmented nevi and has a tendency to tan in some patients.

Genetics

This is an autosomal recessive disorder resulting from mutations in SLC24A5 (15q21.1).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No effective treatment is available.  Visual function can be improved with low vision aids.

References
Article Title: 

SLC24A5 Mutations are Associated with Non-Syndromic Oculocutaneous Albinism

Morice-Picard F, Lasseaux E, Fran?ssois S, Simon D, Rooryck C, Bieth E, Colin E, Bonneau D, Journel H, Walraedt S, Leroy BP, Meire F, Lacombe D, Arveiler B. SLC24A5 Mutations are Associated with Non-Syndromic Oculocutaneous Albinism. J Invest Dermatol. 2013 Aug 28. [Epub ahead of print] PubMed PMID: 23985994.

PubMed ID: 
23985994

Retinitis Pigmentosa 38

Clinical Characteristics
Ocular Features: 

This is a rare clinically heterogeneous condition in which both rods and cones functions are variably affected.  It is a progressive disorder with children often being aware of night vision difficulties during the latter half of the first decade of life.  Reduced vision is often present at this time as well and progressively deteriorates.  Visual fields are constricted to 20-30 degrees.  Rod responses may be nondetectable in the first decade.

Central vision is subnormal as early as childhood and progressively worsens with age.  Dyschromatopsia to some degree is often present early as well and some patients have a maculopathy with a bull’s eye pattern and thinning of the photoreceptor layer seen on OCT.  Attenuated retinal vessels, pale optic discs, and variable fundus pigmentary changes (including pigmentary mottling and bone spicules) have been seen.  The degree and course of the photoreceptor damage is variable leading some to propose that RP38 is primarily a cone-rod dystrophy.

Systemic Features: 

None

Genetics

This is an autosomal recessive disorder resulting from homozygous mutations in the MERTK gene (2q13).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No treatment has been reported but young people especially could benefit from low vision aids and special education therapy.

References
Article Title: 

Myasthenic Syndromes, Congenital, Including AChR Deficiency

Clinical Characteristics
Ocular Features: 

The congenital myasthenic syndromes are genetically and clinically heterogeneous.  Ptosis is the outstanding ocular sign and virtually always present.  Strabismus and ophthalmoplegia are less common.  These signs are not helpful in the differential diagnosis of the many types of congenital myasthenia.

Some degree of ptosis is usually evident during the first 6 months of life.  By about 2 years of age strabismus and ophthalmoparesis are apparent but this sequence is highly variable.

Systemic Features: 

This is a group of nonprogressive disorders most often associated with acetylcholine receptor (AChR) defects at the neuromuscular junction.  An early sign may be decreased fetal movements.  Generalized weakness, a weak cry, and hypotonia are evident at birth.  Easy fatigability and limb weakness are noted in early childhood and affected children have difficulty running. Facial weakness, dysarthria, weakness of the tongue, and dysphagia are often present and many patients have respiratory difficulties. Motor development can be delayed.  Acute illnesses may exacerbate muscle weakness.

Genetics

This is the most common form of the congenital myasthenic syndromes. It is an autosomal recessive disorder of the postsynaptic type, so called because the mutations occur in genes that encode the subunits of acetylcholine receptors: CHRNE(17P13.2), and CHRNB1(17p13.1).  A similar phenotype results from mutations in MUSK (9p31.3) which is critical for synaptic differentiation.

Mutations in RAPSN(11p11.2), whose protein product is important for stabilization of the acetylcholine receptors at the endplate, may result in a similar phenotype but may also produce the fetal akinesia deformation sequence.  This lethal condition is often associated with severe respiratory disease and dysmorphism including limb contractures, micrognathia, and feeding difficulties.  Nothing is known about the ocular signs.

Another autosomal recessive congenital myasthenic syndrome (610542), CMSTA1, has a somewhat later onset (adolescence) and weakness in a limb girdle distribution but no ptosis or oculomotor problems.  Tubular aggregates of muscle fibers can be seen on biopsy.

Presynaptic autosomal recessive forms of congenital myasthenia such as CMS20 (617143) caused by mutations in SLC5A7 (2q12) and CMS21 (617239) secondary to mutations in SLC18A3 (10q11.23) with severe episodic apnea and ocular signs of ptosis and ophthalmoparesis have been reported.

Other postsynaptic forms of congenital myasthenia are the fast-channel type (FCCNS) (608930) and the slow channel type (SCCMS) (601462).  Ophthalmoparesis occurs early in both types.

The classification of congenital myasthenia syndromes is under construction.  In the case of many types only a single or very few families have been reported.   While the clinical manifestations involve alterations in the neuromuscular junnction, some result from heterozygous mutations while others are due to homozygous changes.  The defect may reside in presynaptic, synaptic, or postsynaptic mechanisms.  For a discussion and comprehensive listing of the various types see 601462.

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

Cholinesterase inhibitor drugs can be highly beneficial in some forms of the disease but genotyping is necessary before attempting pharmacological therapy.  Frequent ventilation and enteric feeding may be helpful for selected individuals.  Individuals should be protected from acute illnesses, especially respiratory infections.

References
Article Title: 

Impaired Presynaptic High-Affinity Choline Transporter Causes a Congenital Myasthenic Syndrome with Episodic Apnea

Bauche S, O'Regan S, Azuma Y, Laffargue F, McMacken G, Sternberg D, Brochier G, Buon C, Bouzidi N, Topf A, Lacene E, Remerand G, Beaufrere AM, Pebrel-Richard C, Thevenon J, El Chehadeh-Djebbar S, Faivre L, Duffourd Y, Ricci F, Mongini T, Fiorillo C, Astrea G, Burloiu CM, Butoianu N, Sandu C, Servais L, Bonne G, Nelson I, Desguerre I, Nougues MC, Boeuf B, Romero N, Laporte J, Boland A, Lechner D, Deleuze JF, Fontaine B, Strochlic L, Lochmuller H, Eymard B, Mayer M, Nicole S. Impaired Presynaptic High-Affinity Choline Transporter Causes a Congenital Myasthenic Syndrome with Episodic Apnea. Am J Hum Genet. 2016 Sep 1;99(3):753-61.

PubMed ID: 
27569547

Congenital myasthenic syndromes

Hanta?O D, Richard P, Koenig J, Eymard B. Congenital myasthenic syndromes. Curr Opin Neurol. 2004 Oct;17(5):539-51. Review.

PubMed ID: 
15367858

Retinal Cone Dystrophy 3B

Clinical Characteristics
Ocular Features: 

This is a degenerative disorder in which patients have a progressive deterioration of visual acuity and color vision.  Most patients have significant myopia.  Visual difficulties begin in early childhood with acuity of 20/100 or worse by the second decade of life.  Color vision deficits can be detected in the second decade but nyctalopia occurs later in young adults.  Photophobia is a prominent symptom.  The ERG shows reduced and delayed cone responses.  Rod responses to low intensity flashes are undetectable but increased stimulus intensity leads to an abrupt increase in amplitude, often exceeding the upper limits of normal.

The fundus appears normal in some patients but foveal or parafoveal atrophy, a macular bull’s eye, hyperfluorescence anomalies, and a generalized fine pigmentary retinopathy have been reported.  There may be some temporal pallor in the optic nerves.  Nystagmus and strabismus may be present.

Systemic Features: 

No systemic disease has been reported.

Genetics

This is an autosomal recessive disorder resulting from homozygous or compound heterozygous mutations in the KCNV2 gene (9p24.2).

Pedigree: 
Autosomal recessive
Treatment
Treatment Options: 

No effective treatment is available for this dystrophy.  Low vision aids and tinted lenses may be helpful.

References
Article Title: 

Charcot-Marie-Tooth Disease(s)

Clinical Characteristics
Ocular Features: 

Optic atrophy is present in some patients, particularly in X-linked recessive (CMTX5; 311070), X-linked dominant (CMTX5; 302800), and autosomal recessive (CMT2A2B; 617087) disease.  Congenital and juvenile-onset open-angle glaucoma has been reported among members of 2 consanguineous families with type 4B2, or CMT4B2; (604563).  The mean age of onset was 8 years.

Systemic Features: 

Charcot-Marie-Tooth disease is a large group of clinically and genetically heterogeneous disorders characterized by progressive motor and sensory polyneuropathy.  These can be separated (with overlap) into two large groups on the basis of electrophysiologic criteria: type 1 is the demyelinating form, and type 2 the axonal form.  Patients with primarily distal motor neuropathy are sometimes considered to comprise a third type.

 Symptoms such as weakness in the extremities and digits have a variable age of onset but usually become evident in late childhood or early adulthood.  Small muscles of the hands and feet are often atrophied to some degree.  Some patients develop hearing loss of the neurosensory type.  Foot deformities such as pes cavus are common.  Nerve conduction velocity (reduction) and electromyography can be helpful diagnostically.  It may be helpful to look for characteristic changes such as loss of myelinated fibers and focal myelin sheath folding in sural nerve biopsies.  Intellectual impairment and dementia are usually not features of Charcot-Marie-Tooth disease.

Hemizygous individuals with X-linked types of CMT such as CMTX2-5 seem to be more likely to have intellectual disabilities, hearing loss, spasticity, and optic neuropathy.

Genetics

Charcot-Marie-Tooth disease can also be classified on the basis of their hereditary patterns including autosomal dominant, autosomal recessive, X-linked recessive, and X-linked dominant.  Each of these contains yet more distinct subtypes as defined by mutations in at least 40 genes.

The wide range of disease severity and the overlapping of many signs can make pedigree construction and the determination of recurrence risks and prognosis challenging.  The only recourse may be genotyping.

See Charcot-Marie-Tooth Disease with Glaucoma (604563) for a form of this disease in which glaucoma occurs early.

Pedigree: 
Autosomal dominant
Autosomal recessive
X-linked dominant, father affected
X-linked dominant, mother affected
X-linked recessive, carrier mother
X-linked recessive, father affected
Treatment
Treatment Options: 

The widespread and debilitating polyneuropathy requires a multidisciplinary management approach with neurologists, physical and occupational therapists, audiologists, pain specialists, and orthopedists.  Pharmaceuticals such as gabapentin may be used for neuropathic pain.  Surgery for pes cavus and joint dysplasias can be helpful.

References
Article Title: 

Charcot-Marie-Tooth disease

Carter GT, Weiss MD, Han JJ, Chance PF, England JD. Charcot-Marie-Tooth disease. Curr Treat Options Neurol. 2008 Mar;10(2):94-102.

PubMed ID: 
18334132

Mutations in MTMR13, a new pseudophosphatase homologue of MTMR2 and Sbf1, in two families with an autosomal recessive demyelinating form of Charcot-Marie-Tooth disease associated with early-onset glaucoma

Azzedine H, Bolino A, Taieb T, Birouk N, Di Duca M, Bouhouche A, Benamou S, Mrabet A, Hammadouche T, Chkili T, Gouider R, Ravazzolo R, Brice A, Laporte J, LeGuern E. Mutations in MTMR13, a new pseudophosphatase homologue of MTMR2 and Sbf1, in two families with an autosomal recessive demyelinating form of Charcot-Marie-Tooth disease associated with early-onset glaucoma. Am J Hum Genet. 2003 May;72(5):1141-53.

PubMed ID: 
12687498

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