What is the most likely diagnosis ?

a Pitted keratolysis

Further assessment

In ED , repeat observations reveal a respiratory rate of 60 with worsening saturations to 92 % on room air and moderate respiratory distress .

Chloe is admitted under the paediatric team for supplemental oxygen , investigation and monitoring . As part of her workup , she has a nasopharyngeal aspirate ( NPA ) for respiratory viral and pertussis PCR , blood tests ( including cultures ), chest X-ray , ECG and echocardiogram .

Her NPA is positive for respiratory syncytial virus ( RSV ). Pathology , blood cultures , chest X-ray and ECG are all unremarkable .

Echocardiography reveals a moderate-sized ventricular septal defect ( VSD ).

Diagnosis

Chloe is diagnosed with RSV bronchiolitis , which has precipitated heart failure associated with a moderate-sized isolated VSD .

Discussion

As we hit the winter months , respiratory illnesses , particularly bronchiolitis , are the most common cause of hospital admission in infancy . The diagnosis of bronchiolitis is clinical , and in the absence of diagnostic uncertainty , deterioration or red

flag features , no investigations or medications are needed . There is no indication for antibiotics , bronchodilators or corticosteroids for bronchiolitis . Moderate to severe cases warrant admission for supplemental oxygen and hydration . ²

Bronchiolitis was certainly the most likely diagnosis to account for the initial presenting features in this case . But it is important to keep in mind the differential diagnoses for infants with poor feeding , wheeze and tachypnoea , which include pneumonia , viral-induced wheeze , congenital heart disease , pertussis , sepsis , bronchial foreign body and metabolic conditions .

A useful mnemonic to aid the clinician in the diagnosis of the unsettled infant is outlined in box 2 . Safety netting , as this GP did , by providing clear , written information to parents about progressive and red flag features and ensuring timely and ongoing follow-up , is another helpful strategy

to ensure these less common , serious diagnoses are not missed .

VSDs are one of the most common cardiac defects , affecting between 1.7 and 53 in every 1000 live births . ⁴ They may occur in isolation , in combination with other congenital heart defects , or as part of an underlying genetic or chromosomal syndrome . The natural history depends on the size and location of the defect and degree of associated left to right shunting . Small defects are usually asymptomatic and are typically diagnosed when a murmur is identified in the first weeks of life , in an otherwise well infant . ⁵ Moderate to large VSDs usually present in the first month of life with symptoms of heart failure , including tachypnoea , tachycardia , poor feeding or weight gain and respiratory distress . Infants may become tachypnoeic , sweaty and tired with feeding . ⁴ The clinical presentation depends on the degree of left to right shunting . In extreme circumstances , infants can present with systemic-to-pulmonary cardiovascular communication , pulmonary arterial disease , and cyanosis ( Eisenmenger ’ s syndrome ). ⁴

Large VSDs can lead to pulmonary hypertension , aortic valve prolapse and congestive cardiac failure , in which case surgical repair is indicated .

That said , most VSDs close spontaneously with less than 10 % needing surgical repair . ⁴

In symptomatic patients , medical management aims to alleviate symptoms of heart failure and normalise growth , and to prevent or postpone the need for surgery . This may require diuretic therapy and nutritional support . Preventive measures to reduce the risk of respiratory infection , such as influenza immunisation , are also recommended . ⁶

Outcome

Chloe clinically improves with only supplemental oxygen required . She is discharged after a week with close paediatric follow-up as an outpatient .

References on request from kate . kelso @ adg . com . au

A day after being diagnosed with bronchiolitis , the infant appeared to be barely breathing and became pale and floppy .

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b Plantar warts

c Dishydrotic eczema

d Tinea pedis

ANSWER The answer is a . Pitted keratolysis is a superficial bacterial skin infection , typically affecting the soles of the feet . The characteristic features are skin whitening , clusters of punched-out pits , and offensive odour . ^{1 , 2} The pits and craters result from destruction of the stratum corneum by bacterial protease enzymes . The most common causative organisms are corynebacterium , Kytococcus sedentarius , Dermatophilus congolensis , actinomyces and streptomyces . These organisms release sulfur compounds , resulting in the tell-tale odour .

Risk factors include regular use of occlusive footwear , hot and humid conditions and plantar hyperhidrosis . The condition may also occur in association with diabetes or immunodeficiency . ^{1 , 2}

The diagnosis is typically clinical ; however , if there is any uncertainty , skin swab for culture may identify a causative organism , and biopsy may show dense groups of bacteria in the stratum corneum . 1 The differential diagnosis includes intertrigo , tinea pedis , eczema , punctate palmoplantar keratoderma and plantar warts . ^{1 , 2}

Topical antibiotics — such as erythromycin , clindamycin or mupirocin — and antiseptics , such as benzoyl peroxide , are effective for treatment . Hygiene measures are also important for treatment and to prevent recurrence . These include limiting the use of occlusive footwear , drying of shoes after exercise , wearing sweat-absorbing socks and cleaning and drying the feet after exercise . Underlying hyperhidrosis also warrants treatment with twice weekly foot antiperspirant . Any contributing immune factors should be addressed . ¹

Plantar warts may coalesce to form mosaic plaques that resemble pitted keratolysis . A differentiating feature of warts is the presence of thrombosed capillaries , particularly after the stratum corneum is pared .

Dyshidrotic eczema typically causes pruritis and tense deepseated vesicles , with a predilection to lateral aspects of digits .

Tinea pedis usually presents with macerated and erythematous plaques between the toes , with fine scale on the plantar and lateral surfaces or vesicobullous eruption on the instep . Fungal hyphae will be present on potassium hydroxide preparation or culture . ³ Dr Kate Kelso is a GP and medical editor at Australian Doctor .

References on request from kate . kelso @ adg . com . au