Diffuse panbronchiolitis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief:

Diffuse panbronchiolitis (DPB)^[1] is an idiopathic (of unknown cause) inflammatory lung disease,^[2] considered to be a type of COPD.^[3][4] It is a severe, progressive form of bronchiolitis, mainly affecting the respiratory bronchioles (the section of the bronchioles involved in gas exchange).^[2]

The term “diffuse” refers to the lesions which appear throughout both lungs, while the term “pan-“ refers to the inflammation found in all layers of the respiratory bronchioles, both terms describing a common pathology for the disease.^[2]

If left untreated, DPB is fatal, usually progressing to bronchiectasis, an irreversible lung conditon that causes respiratory failure.^[2]

• [Disease name] was first discovered by [scientist name], a [nationality + occupation], in [year] during/following [event].
• In [year], [gene] mutations were first identified in the pathogenesis of [disease name].
• In [year], the first [discovery] was developed by [scientist] to treat/diagnose [disease name].

• [Disease name] may be classified according to [classification method] into [number] subtypes/groups:

• [group1]
• [group2]
• [group3]

• Other variants of [disease name] include [disease subtype 1], [disease subtype 2], and [disease subtype 3].

• The pathogenesis of [disease name] is characterized by [feature1], [feature2], and [feature3].
• The [gene name] gene/Mutation in [gene name] has been associated with the development of [disease name], involving the [molecular pathway] pathway.
• On gross pathology, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].
• On microscopic histopathological analysis, [feature1], [feature2], and [feature3] are characteristic findings of [disease name].

• [Disease name] may be caused by either [cause1], [cause2], or [cause3].
• [Disease name] is caused by a mutation in the [gene1], [gene2], or [gene3] gene[s].
• There are no established causes for [disease name].

• [Disease name] must be differentiated from other diseases that cause [clinical feature 1], [clinical feature 2], and [clinical feature 3], such as:

• [Differential dx1]
• [Differential dx2]
• [Differential dx3]

• The prevalence of [disease name] is approximately [number or range] per 100,000 individuals worldwide.
• In [year], the incidence of [disease name] was estimated to be [number or range] cases per 100,000 individuals in [location].

• Patients of all age groups may develop [disease name].

• [Disease name] is more commonly observed among patients aged [age range] years old.
• [Disease name] is more commonly observed among [elderly patients/young patients/children].

• [Disease name] affects men and women equally.

• [Gender 1] are more commonly affected with [disease name] than [gender 2].
• The [gender 1] to [Gender 2] ratio is approximately [number > 1] to 1.

• There is no racial predilection for [disease name].

• [Disease name] usually affects individuals of the [race 1] race.
• [Race 2] individuals are less likely to develop [disease name].

• Common risk factors in the development of [disease name] are [risk factor 1], [risk factor 2], [risk factor 3], and [risk factor 4].

• The majority of patients with [disease name] remain asymptomatic for [duration/years].
• Early clinical features include [manifestation 1], [manifestation 2], and [manifestation 3].
• If left untreated, [#%] of patients with [disease name] may progress to develop [manifestation 1], [manifestation 2], and [manifestation 3].
• Common complications of [disease name] include [complication 1], [complication 2], and [complication 3].
• Prognosis is generally [excellent/good/poor], and the [1/5/10­year mortality/survival rate] of patients with [disease name] is approximately [#%].

• The diagnosis of [disease name] is made when at least [number] of the following [number] diagnostic criteria are met:

• [criterion 1]
• [criterion 2]
• [criterion 3]
• [criterion 4]

• [Disease name] is usually asymptomatic.
• Symptoms of [disease name] may include the following:

• [symptom 1]
• [symptom 2]
• [symptom 3]
• [symptom 4]
• [symptom 5]
• [symptom 6]

• Patients with [disease name] usually appear [general appearance].
• Physical examination may be remarkable for:

• [finding 1]
• [finding 2]
• [finding 3]
• [finding 4]
• [finding 5]
• [finding 6]

• There are no specific laboratory findings associated with [disease name].

• A [positive/negative] [test name] is diagnostic of [disease name].
• An [elevated/reduced] concentration of [serum/blood/urinary/CSF/other] [lab test] is diagnostic of [disease name].
• Other laboratory findings consistent with the diagnosis of [disease name] include [abnormal test 1], [abnormal test 2], and [abnormal test 3].

• There are no [imaging study] findings associated with [disease name].

• [Imaging study 1] is the imaging modality of choice for [disease name].
• On [imaging study 1], [disease name] is characterized by [finding 1], [finding 2], and [finding 3].
• [Imaging study 2] may demonstrate [finding 1], [finding 2], and [finding 3].

• [Disease name] may also be diagnosed using [diagnostic study name].
• Findings on [diagnostic study name] include [finding 1], [finding 2], and [finding 3].

• There is no treatment for [disease name]; the mainstay of therapy is supportive care.

• The mainstay of therapy for [disease name] is [medical therapy 1] and [medical therapy 2].
• [Medical therapy 1] acts by [mechanism of action 1].
• Response to [medical therapy 1] can be monitored with [test/physical finding/imaging] every [frequency/duration].

• Surgery is the mainstay of therapy for [disease name].
• [Surgical procedure] in conjunction with [chemotherapy/radiation] is the most common approach to the treatment of [disease name].
• [Surgical procedure] can only be performed for patients with [disease stage] [disease name].

• There are no primary preventive measures available for [disease name].

• Effective measures for the primary prevention of [disease name] include [measure1], [measure2], and [measure3].

• Once diagnosed and successfully treated, patients with [disease name] are followed-up every [duration]. Follow-up testing includes [test 1], [test 2], and [test 3].

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief:

DPB remains idiopathic, which means an exact physiological, environmental, or pathogenic cause of the disease is unknown.^[1] However, several known factors are involved with the pathogenesis of DPB.^[2][3]

The major histocompatibility complex (MHC) is a large genomic region found in most vertebrates, that is associated with mating and the immune system. It is located on chromosome 6 in humans. A subset of the human MHC is human leukocyte antigen (HLA), which controls the antigen presenting system, as part of adaptive immunity against pathogens such as bacteria and viruses.

Genetic predisposition for DPB has been localized to two HLA haplotypes unique to Asians, particularly of East Asian descent.^[2][4] HLA-B54 is associated with DPB in Japanese patients,^[2] while HLA-A11 is associated with the disease in Koreans.^[3] One or more candidate genes^[5] (a gene suspected to be responsible for a trait or disease) within this region of class I HLA are believed to be the genetic factor responsible for DPB, allowing disease susceptibility^[4] related to the structure of the antigen presenting molecules selected by these genes.^[6]

Candidate genes within HLA that are most likely involved with DPB suceptibility include: C6orf37^[5] and TAP2.^[6]

Another such gene, though not a part of the HLA system, is the gene for interleukin 8 (IL-8)^[7] located on chromosome 4. The role of IL-8 to produce inflammation by causing the proliferation of neutrophil granulocytes at any site of pathogenic involvement, in conjunction with strong microsatellite identification with DPB, implicates IL-8 as another candidate gene associated with DPB pathogenesis.^[7] This also supports the idea that several factors, including those unrelated to HLA as well as non-genetic, and unknown factors, may cause the disease.^[7]

The inflammation common to DPB also provides a means to determine other mechanisms of disease pathogenesis.^[8] This may be partly due to the persistence of inflammation in DPB, with or without the presence of the two opportunistic bacteria sometimes found with the disease (haemophilus influenzae, pseudomonas aeruginosa).^[9] Inflammation caused by the chemokine MIP-1alpha and its involvement with CD8+ T-cells is believed to be one such mechanism of DPB pathogenesis.^[8]

Other factors found with DPB play a part in its pathogenesis by sometimes causing minor variations of it.

Beta defensins, a family of antimicrobial peptides found in the respiratory tract, are responsible for further inflammation in DPB, when associated pathogens like pseudomonas aerugenosa are present.^[10]

If present in a DPB patient, the human T-lymphotropic virus, type I, a retrovirus, modifies DPB pathogenesis by infecting CD4+ cells (Helper T-cells) and altering there effectiveness in reducing both known and unknown pathogenic involvement with DPB.^[11] Conversely, an onset of DPB causes increased frequency of Adult T-cell leukemia in human lymphotropic virus sufferers.^[11]

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DPB has the highest incidence among Japanese.^[1][2][3] Korean,^[4][5][6] Chinese^[3][7] and Thai cases^[8] have been reported as well. A genetic predisposition among East Asians is indicated,^[9][5][6] with a lower worldwide prevalence of DPB still usually related to Asian ancestry.^[10] However, rare cases of DPB, being those in the western world in individuals with non-Asian lineage,^[11] have also been noted.^[12][13][11]

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief:

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