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Hereditary neuropathy v1.500 PPOX Sharon Whatley changed review comment from: Relevant metabolic investigation: urine porphobilinogen (to be completed before genetic testing for diagnosis of an acute porphyric attack) plasma porphyrin fluorescence emission (homozygous VP).
PMID: 38940544 Aarsand reports that variegate porphyria (VP) is an autosomal dominant disorder and estimates that individuals with a predisposition for VP in the general population is 1/3,000 (except where founder effects occur e.g. South Africa). A rough estimate of the penetrance of pathogenic variants in this gene is given as 1%. Due to this low penetrance, genetic testing alone may be misleading and cause misdiagnosis. IPNET advises that VP is diagnosed using biochemical tests (urine porphobilinogen during an acute attack followed by plasma fluorescence emission or if the patient only has cutaneous symptoms plasma porphyrin fluorescence) as the penetrance is so low.
PMID: 35584894 Schulenburg-Brand reviews the neuropathy that may occur in the acute porphyrias. Weakness and altered sensation are typically mild in an acute attack and improve as the pain resolves. In a small number of cases, severe, progressive peripheral neuropathy develops. Neuropathy can worsen, even after the acute pain resolves, with a Guillain-Barré like picture. Proximal muscle weakness occurs in the upper limbs and can progress to involve the legs and cause respiratory failure. Cranial nerves can be involved, with the facial, vagus and hypoglossal nerves most often affected, causing swallowing difficulties. Sensory neuropathy is less common, but can cause numbness over the torso and thighs, sometimes with severe pain. Cases gradually resolve with respiratory support, and some patients may need prolonged mechanical ventilation. After recovery, some degree of peripheral neuropathy can persist, with foot drop and wrist drop being fairly typical.
PMID: 37879139 Assaleh reports that biallelic VP is rare. To the best of our knowledge there are 25 patients (in 21 families) reported with homozygous VP (40114189 Kaiser 37879139 Assaleh, 33159949 Cho and references therein). It usually presents in infancy with severe cutaneous manifestations. Three of these patients (PMID: 11286631 Kauppinen, 10870850 Corrigall, 8290408 Hift) had sensory neuropathy.
PMID:11286631 Kauppinen reports a patient who following birth presented with severe bullous skin disease followed by increased fragility and keloid-like scarring. His fingers were shortened. Mental status, EEG, and CT of the head were normal, but sensory polyneuropathy was shown in especially in the upper extremities. Fine motor coordination disturbances were accompanied by minor verbal and visuospatial deficiencies. DNA from the patient showed that he is compound heterozygous for PPOX: c.35T>C, p.(Ile12Thr) and c.767C>G, p.(Pro256Arg).
PMID:10870850 Corrigall reports a 10-month-old child with fragile skin with blisters, scars, and milia most marked in sun-exposed areas. She had brachydactyly, photo-onycholysis, myopia, nystagmus, a sensory neuropathy and problems with concentration. She never had a typical acute attack. Genetic analysis showed that this patient was compound heterozygous for PPOX c.175C>T, p.(Arg59Trp) and c.1043A>G, p.(Tyr348Cys).
PMID: 8290408 Hift reports child who within days of birth developed severe blistering of the face and hands. She had brachydactyly, severe myopia and a pendular nystagmus. Neurological development was delayed with normal intelligence. She had gross sensory neuropathy of the hands and feet but no acute attacks.
Careful consideration should be given to the reporting of a single pathogenic variant as an incidental finding in the PPOX gene, due to its low clinical penetrance.; to: Relevant metabolic investigation: urine porphobilinogen (to be completed before genetic testing for diagnosis of an acute porphyric attack) plasma porphyrin fluorescence emission (homozygous VP).
PMID: 38940544 Aarsand reports that variegate porphyria (VP) is an autosomal dominant disorder and estimates that individuals with a predisposition for VP in the general population is 1/3,000 (except where founder effects occur e.g. South Africa). A rough estimate of the penetrance of pathogenic variants in this gene is given as 1%. Due to this low penetrance, genetic testing alone may be misleading and cause misdiagnosis. IPNET advises that VP is diagnosed using biochemical tests (urine porphobilinogen during an acute attack followed by plasma fluorescence emission or if the patient only has cutaneous symptoms plasma porphyrin fluorescence) as the penetrance is so low.
PMID: 35584894 Schulenburg-Brand reviews the neuropathy that may occur in the acute porphyrias. Weakness and altered sensation are typically mild in an acute attack and improve as the pain resolves. In a small number of cases, severe, progressive peripheral neuropathy develops. Neuropathy can worsen, even after the acute pain resolves, with a Guillain-Barré like picture. Proximal muscle weakness occurs in the upper limbs and can progress to involve the legs and cause respiratory failure. Cranial nerves can be involved, with the facial, vagus and hypoglossal nerves most often affected, causing swallowing difficulties. Sensory neuropathy is less common, but can cause numbness over the torso and thighs, sometimes with severe pain. Cases gradually resolve with respiratory support, and some patients may need prolonged mechanical ventilation. After recovery, some degree of peripheral neuropathy can persist, with foot drop and wrist drop being fairly typical.
PMID: 37879139 Assaleh reports that biallelic VP is rare. To the best of our knowledge there are 25 patients (in 21 families) reported with homozygous VP (40114189 Kaiser 37879139 Assaleh, 33159949 Cho and references therein). It usually presents in infancy with severe cutaneous manifestations. Three of these patients (PMID: 11286631 Kauppinen, 10870850 Corrigall, 8290408 Hift) had sensory neuropathy, as reported by the previous reviewer.

Careful consideration should be given to the reporting of a single pathogenic variant as an incidental finding in the PPOX gene, due to its low clinical penetrance.
Hereditary neuropathy v1.500 PPOX Sharon Whatley reviewed gene: PPOX: Rating: GREEN; Mode of pathogenicity: None; Publications: 38940544, 35584894, 37879139, 11286631, 10870850, 8290408; Phenotypes: ; Mode of inheritance: BOTH monoallelic and biallelic (but BIALLELIC mutations cause a more SEVERE disease form), autosomal or pseudoautosomal
Hereditary neuropathy v1.470 PPOX Achchuthan Shanmugasundram Mode of inheritance for gene: PPOX was changed from MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted to BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Hereditary neuropathy v1.469 PPOX Achchuthan Shanmugasundram Tag Q3_23_MOI was removed from gene: PPOX.
Hereditary neuropathy v1.469 PPOX Achchuthan Shanmugasundram changed review comment from: Comment on mode of inheritance: There are at least three cases of variegate porphyria reported with biallelic variants in PPOX gene and sensory neuropathy. Hence, the MOI can be updated from "MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted" to "BOTH monoallelic and biallelic, autosomal or pseudoautosomal" in the next GMS review.; to: Comment on mode of inheritance: There are at least three cases of variegate porphyria reported with biallelic variants in PPOX gene and sensory neuropathy. Hence, the MOI should be updated from "MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted" to "BOTH monoallelic and biallelic, autosomal or pseudoautosomal".
Hereditary neuropathy v1.469 PPOX Achchuthan Shanmugasundram Tag Q3_23_MOI tag was added to gene: PPOX.
Hereditary neuropathy v1.469 PPOX Achchuthan Shanmugasundram Added comment: Comment on mode of inheritance: There are at least three cases of variegate porphyria reported with biallelic variants in PPOX gene and sensory neuropathy. Hence, the MOI can be updated from "MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted" to "BOTH monoallelic and biallelic, autosomal or pseudoautosomal" in the next GMS review.
Hereditary neuropathy v1.469 PPOX Achchuthan Shanmugasundram Mode of inheritance for gene: PPOX was changed from MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Hereditary neuropathy v1.468 PPOX Achchuthan Shanmugasundram Publications for gene: PPOX were set to 8290408; 10870850; 11286631
Hereditary neuropathy v1.467 PPOX Achchuthan Shanmugasundram Publications for gene: PPOX were set to
Hereditary neuropathy v1.466 PPOX Achchuthan Shanmugasundram edited their review of gene: PPOX: Changed rating: GREEN
Hereditary neuropathy v1.466 PPOX Achchuthan Shanmugasundram reviewed gene: PPOX: Rating: ; Mode of pathogenicity: None; Publications: 8290408, 10870850, 11286631; Phenotypes: Porphyria variegata, OMIM:176200, Sensory neuropathy, HP:0000763; Mode of inheritance: BOTH monoallelic and biallelic, autosomal or pseudoautosomal
Hereditary neuropathy v1.353 PPOX Louise Daugherty Source Expert Review Green was added to PPOX.
Rating Changed from Red List (low evidence) to Green List (high evidence)
Hereditary neuropathy v1.352 PPOX Louise Daugherty edited their review of gene: PPOX: Added comment: The Neurology Specialist Test Group agreed that this gene was recommended for the WGS panel based on a broader phenotype view to include conditions where neuropathy is part of a more complex phenotype or where there is overlap with another neurological presentation eg. HSP. This panel includes conditions where neuropathy is part of a more complex phenotype or where there is overlap with another neurological presentation. This panel as going to be used for R78, but subsequently during the follow up call on 21st June with the Test Group it was agreed that it was more clinically relevant for R78 to be restricted to genes that are associated with isolated neuropathy and as a result a new panel was created https://panelapp.genomicsengland.co.uk/panels/846/ for this purpose.; Changed rating: GREEN
Hereditary neuropathy v1.320 PPOX Louise Daugherty Deleted their comment
Hereditary neuropathy v1.300 PPOX Louise Daugherty commented on gene: PPOX: Review and rating uploaded from file (Curation_Template_GMS_Neuro_AR_20190521.xlsx) submitted by Alex Rossor (UCL Institute of Neurology) on behalf of London North GLH for GMS Neurology specialist test group.
Hereditary neuropathy v1.300 PPOX Louise Daugherty reviewed gene: PPOX: Rating: AMBER; Mode of pathogenicity: ; Publications: ; Phenotypes: ; Mode of inheritance:
Hereditary neuropathy v1.167 PPOX Louise Daugherty Phenotypes for gene: PPOX were changed from to Porphyria variegata, 176200; Skin photosensitivity. Acute episodes similar to AIP
Hereditary neuropathy v1.166 PPOX Louise Daugherty Mode of inheritance for gene: PPOX was changed from to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Hereditary neuropathy v1.121 PPOX Alexander Rossor reviewed gene: PPOX: Rating: GREEN; Mode of pathogenicity: ; Publications: ; Phenotypes: Skin photosensitivity. Acute episodes similar to AIP.; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted
Hereditary neuropathy v1.119 PPOX Louise Daugherty Source NHS GMS was added to PPOX.
Hereditary neuropathy v1.118 PPOX Louise Daugherty gene: PPOX was added
gene: PPOX was added to Hereditary neuropathy. Sources: London North GLH
Mode of inheritance for gene: PPOX was set to